Angular Velocity Stepping and Methods of Use in Turbomachinery

ABSTRACT

Provided is an improved architecture for rotary kinetic fluid motors and pumps, in which working fluid gains or loses pressure by flowing through an alternating sequence of radial-flow impellers and radial-flow fluid vortices, the impellers and fluid vortices all rotating around a single axis and in a common direction at staggered speeds, each vortex being the product of rotating fluid that is flowing radially through a bladeless annular volume.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/991,487, filed Jan. 8, 2016, which application claims the benefit ofU.S. Provisional Application 62/169,016, filed Jun. 1, 2015, entitledAngular Velocity Stepping and Methods of Use in Turbomachinery and U.S.Provisional Application 62/183,816, filed Jun. 24, 2015, entitledAngular Velocity Stepping and Methods of Use in Turbomachinery. Each ofthese applications is incorporated herein by reference.

1.) INTRODUCTION

Structure

Provided is an improved architecture for rotary kinetic fluid motors andpumps, in which working fluid gains or loses pressure by flowing throughan alternating sequence of radial-flow impellers and radial-flow fluidvortices, the impellers and fluid vortices all rotating around a singleaxis and in a common direction at staggered speeds, each vortex beingthe product of rotating fluid that is flowing radially through abladeless annular volume.

Function

Each impeller directs working fluid into a radial flow through anaxisymmetric set of substantially radial blades, which requires torqueexchange and therefore power exchange between impeller and fluid. Eachbladeless annular volume directs working fluid flow in a radialdirection through a vortex of substantially uniform fluid angularmomentum, which transitions the fluid's rotational speed from that of anupstream impeller to that of a faster or slower downstream impeller. Thealternating sequence of impeller, vortex, impeller, etc. can transitionworking fluid up to, and down from, the high rotational speeds needed toproduce substantial centripetal pressure change. This architectureoffers significantly higher isentropic efficiencies and a dramaticallyexpanded operational envelope, relative to existing technologies.

2.) BACKGROUND OF THE INVENTION

2.1) Basic Principles of the Technology

In this specification, the term turbomachine refers to any machine that:(1) ingests, contains and discharges a continuous flow of liquid, vaporand/or gas, known as working fluid, (2) uses rotating components incontact with the flow of working fluid to generate localized regions ofaccelerating fluid, and (3) aligns these localized fluid accelerationsand their associated fluid pressure gradients to sustain an overallfluid pressure difference between the device's intake and dischargesections. By using rotating parts to sustain a pressure rise or dropwithin a steady flow, turbomachines continuously transfer energy betweenshafts and fluid. Examples include: primary components of gas turbinesand aerospace turbine engines of any type, steam turbines,turbochargers, axial or centrifugal compressors, hydroelectric turbines,air turbines, dynamic pumps for water or other liquids, etc. NOTE: theterm acceleration as used here refers to any type of change in velocityover time.

Equilibrium requires that any volume of accelerating fluid contain apressure gradient that is aligned with the direction of acceleration,just as Earth's atmosphere and oceans contain vertical pressuregradients caused by its gravity. Severity, or slope, of a pressuregradient is equal to local fluid density multiplied by localacceleration—within turbomachines local acceleration is proportional tolocal blade speed. Mathematical integration of the slope function withrespect to distance along the acceleration vector yields the total fluidpressure difference across the gradient: this forms the unit basis fortotal pressure differences across entire machines. The size of fluidpressure rise or drop that can be generated across a given machine istherefore a function of how fast its blades can spin.

(FIGS. 2A, 2B and 3A) Turbomachines can be broadly divided into twotypes: (1) pumps or compressors that consume shaft power to add energyto fluid flows, by ingesting low-pressure fluid and discharginghigh-pressure fluid, and (2) motors or turbines that extract energy fromfluid flows to produce shaft power, by ingesting high-pressure fluid anddischarging low-pressure fluid. Within both broad types, two distinctmethods are used for creating localized regions of accelerating fluid:(1) Linear Acceleration—Converging 101 or diverging 102 flow passages,whose cross-section areas get larger or smaller along the flow directionto force inverse flow velocity changes as needed to satisfy masscontinuity, are used throughout axial-flow devices and in the impellerintake and discharge sections of centrifugal devices. Fluid pressuredrops during flow through a converging passage, and rises during flowthrough a diverging passage. (2) Centripetal Acceleration—Rotatingradial flow passages 103 displace fluid mass through a centripetalacceleration field and are used within the rotors of centrifugaldevices. Fluid pressure rises during radially outward flow 104, anddrops during radially inward flow. Fluid flow passages are generallydelineated by axisymmetric blade sets or their equivalent, end walls,shrouds and casings: blades are the primary structure responsible forexchanging energy with the fluid, while end walls, shrouds and casingsdirect and constrain flow as it enters, transits and exits each set ofblades. NOTE: within this disclosure, the term converging or divergingflow passage refers only to flow conduits that are intended tomanipulate flow velocities, not those intended to accommodate varyingfluid densities.

(FIGS. 1A through 3C) Turbomachines generally use an alternating patternof rotating 105 and stationary 106 blade sets such that working fluidflows through a stationary set before or after it flows through eachrotating set. This alternating pattern is associated with the use ofconverging or diverging flow passages, for reasons best illustratedusing vector geometry: A vector 107 describing the angle and speed atwhich fluid approaches the leading edges of a given set of blades 108 isdeviated from the vector 109 at which that fluid left the trailing edgesof the immediate upstream blade set 110, that deviation being equal tothe vector 111 describing the speed and direction of the rotating bladeset. This is vector addition: the upstream blade departure vector plusthe blade rotation vector equals the downstream blade approach vector.In compressors 112, the flow vector deviation occurring between adjacentblade sets is a means for boosting the flow velocity 113 entering eachblade set so as to boost the pressure rise that can be produced acrossthe curved diverging flow passages 102 within each blade set. Inturbines 114, the vector deviation between blade sets is a means forconsuming the excess flow velocity 115 leaving the curved convergingflow passages 101 within each blade set. Converging or diverging flowpassages within turbomachines are always associated with the interfacebetween rotating and stationary blade sets, and they exist in every typeof turbomachine. Even radial-flow devices that employ regions ofcentripetal fluid acceleration 103 within their impellers 116 must alsoaddress flow vector deviation due to impeller rotation at impellerintake 117 and discharge 118 sections, and must therefore employconverging or diverging 119 flow passages at or near those locations.

2.2) A Need for Improvement

-   -   2.2.1—Two Basic Problems

(FIGS. 2A and 2B) Total dependence on converging or diverging flowpassages creates two major problems. First, all turbomachines suffersubstantial loss of energy by the action of velocity-dependentmechanisms. This is referred to as the velocity-dependent energy lossproblem in this specification. This type of flow passage generates fluidpressure rise or drop by converting flow kinetic energy into pressure orvice-versa: the generation of a large pressure rise across a divergingflow passage 102 requires a large drop in flow velocity (113 vs. 120)across that passage, while a large pressure drop in a converging flowpassage 101 corresponds to a large flow velocity boost (121 vs. 115).Large fluid pressure changes across individual flow passages aredesirable or even necessary for many turbomachinery applications; thecorresponding large flow velocity changes require the presence of highflow velocities somewhere in these passages. Highest flow velocities aretypically near leading edges 122 of compressor blades and near trailingedges 123 of turbine blades. High flow velocities across adjacent solidsurfaces impose high rates of shear within fluid boundary layers at thefluid-solid interface. High fluid shearing rates cause substantialviscous energy loss and may result in the formation of turbulentboundary layers that make the problem worse. Where compressible fluidsmove past solid structures at transonic or supersonic velocities, shockwaves will form that cause further energy loss. To top it off, thediverging flow passages in compressors can suffer the counter-productiveeffects of fluid boundary layers thickening and possibly separating fromtheir fluid-solid interfaces, creating zones of flow reversal andre-circulation and generally causing unacceptable flow instability.Turbulent boundary layers can only partially mitigate the boundary layerseparation problem. To prevent separation, fluid pressure rise withinindividual flow passages must be kept below a modest limiting value, somore blade sets are needed to produce a given overall pressure rise.This is why compressors are generally larger and less efficient thanequivalent turbines. The net result of viscous shear loss, turbulentloss, shock loss and boundary layer thickening/separation is asubstantial reduction in machine efficiency. The most efficientturbomachines in existence suffer total losses in the range of 10-20% oftotal energy exchanged. Although 10-20% may sound relatively small, suchlosses can have major consequences for the operation of these devices,as will be demonstrated.

The second major problem caused by converging or diverging flow passagesis the relative inability of turbomachines to handle widely varyingfluid flow rates without also changing blade RPM proportionately. Putanother way, use of converging or diverging flow passages in aturbomachine limits to what extent the blade RPM and the machine flowrate can vary independently of one another. Since blade RPM determinesthe amount of total fluid pressure rise or drop that can be producedacross a given machine, this problem is therefore referred to as theflow-pressure coupling problem in this specification. Because of it, theamount of total pressure rise or drop any turbomachine can produce is atleast partially dependent on how much fluid is flowing through thatmachine. There are two reasons for this coupling.

(FIGS. 2A, 2B and 4) The primary reason converging or diverging flowpassages cause flow-pressure coupling is their association with thealternating patterns of rotating and stationary blade sets detailedabove. Vector geometry again offers useful explanation: as before, thefluid's approach vector 124 at downstream blades is equal to the vectorsum of (1) that fluid's departure vector 125 at upstream blades and (2)the blade rotation vector 126 of either upstream or downstream blades.The magnitude of the blade rotation vector is a direct function of bladeRPM, while the magnitude of the upstream blade departure vector is adirect function of fluid flow rate through the machine. The vectortriangles (e.g., 107-109-111) shown in the drawings represent vectoraddition: the reader can see that the direction of the downstreamapproach vector 124 is heavily dependent on the relative magnitudes ofthe other two vectors 125, 126, since the triangle must always close.The angle at which fluid flow approaches blade leading edges istherefore heavily dependent on relative values of machine flow rate andblade RPM. If either the upstream departure vector 125 or the bladerotation vector 126 shortens or lengthens significantly while the otherremains unchanged, the downstream flow approach angle changessignificantly 127, 128. This becomes a problem because smooth flow intoa blade set requires that blade entry surfaces 129 near leading edges besubstantially aligned with flow approach vectors. Although some newerturbomachinery designs incorporate variable-angle stationary blades toaccommodate variable flow approach vectors, orientations of rotatingblades cannot realistically be altered. Fixed blade orientations limitthe permissible variation in flow approach angle 130, because severeflow turbulence and flow instability will form near leading edges 129 ifflow approach vectors 124 come substantially out of alignment with bladeentry surfaces. This will cause unacceptable energy losses and, in thecase of compressors, could de-stabilize operation. Efficient andreliable turbomachinery operation therefore requires that anysignificant variations in machine flow rate be accompanied by someproportional variation in blade RPM and therefore in total fluidpressure rise/drop.

The secondary reason converging or diverging flow passages causeflow-pressure coupling in turbomachines is the very nature of the taskthey perform: conversion of the kinetic energy of flow into fluidpressure or vice-versa. Because these flow passages generally have fixedgeometries, mass continuity requires that the ratio of inlet-to-outletflow velocities across a given passage also be fixed, assuming constantfluid density. In contrast, the quantity of fluid pressure rise/dropthat can be produced across one of these passages is a function of thedifference between inlet and outlet flow velocities, not the ratio ofthe two. This distinction is important: higher fluid flow rates througha converging or diverging passage dictate proportionately higher flowvelocities at every point along that passage and therefore a largerinlet-to-outlet flow velocity difference for a fixed passage geometry.Similarly, lower flow rates dictate proportionately lower flowvelocities at every point and therefore a smaller inlet-to-outlet flowvelocity difference. Pressure change within the machine thereforebecomes dependent on fluid flow rate through the machine.

-   -   2.2.2—Consequences of the Two Problems

Major operational constraints result from the problem ofvelocity-dependent energy loss in turbomachines. Perhaps the bestexample to demonstrate these constraints is the Brayton cycle heatengine. All gas turbine type engines use some variation of the Braytonthermodynamic cycle. This cycle's sequence of events is: (1) anisentropic compression of a gas such as air, (2) a constant-pressureheat addition to the gas at high temperatures, (3) an isentropicexpansion of the gas, and (4) a constant-pressure heat rejection fromthe gas at low temperatures to finish the cycle. The isentropicexpansion generally occurs within a turbine and results in theproduction of shaft power. The isentropic compression generally occurswithin a turbocompressor and requires consumption of the shaft powerproduced by the turbine. The cycle's net useful output can take the formof leftover turbine shaft power not used by the compressor, or it cantake the form of higher gas pressures exiting the engine than enteringit, such as in aircraft jet propulsion. The ideal thermal efficiency ofthis cycle is proportional to the ratio of the highest to lowest gaspressures in the cycle. Several industries that use gas turbines, suchas air transport and electric utilities, experience significant marketpressure to operate machines of the highest possible thermal efficiency.Since thermal efficiency is tied to cycle pressure ratio, the long-termtrend in gas turbine design has been toward greater and greater cyclepressure ratios and therefore larger pressure rise across the compressorand larger drop across the turbine. This trend has compounded the energyloss problem in those components, because at higher cycle pressureratios the shaft power transmitted from turbine to compressor can bevery large relative to the thermal power input at the high-temperatureheat addition. Total energy losses in turbine and compressor areproportional to transmitted shaft power but are deducted from thermalpower input, which is the only energy input to the system. So if aparticular gas turbine engine suffers 10% losses in both turbine andcompressor and transfers twice as much power between the two as it takesin at the high-temperature heat addition, that engine will suffer athermal efficiency penalty of approximately 2×(10%+11.1%)=42% purely asa result of the losses in turbine and compressor. If the same enginetransmits three times as much power on shafts as it takes in as thermalinput, the 10% losses will manifest as an efficiency loss of roughly 63%to the engine. In this way the efficiency gains realized by higher cyclepressure ratios can be diminished or even wiped out by compounded energylosses in turbomachine elements.

To counter the problem of compounded losses, a second long-term trend ingas turbine design has followed in lock-step with the first: increasingthermal power input to the cycle to offset compounded energy losses fromhigher cycle pressure ratio. Increasing thermal power input to afixed-flow Brayton cycle means a larger temperature rise across the heataddition section and therefore a higher gas temperature at the turbineintake. Very high turbine intake temperatures are a reality in almostall modern gas turbine designs and are one of the primary drivers ofdesign and manufacturing costs, of maintenance/overhaul requirements andof lifespan limitations for turbine-type engines. To understand why, oneneed only appreciate that first-stage turbine blades are required towithstand tens or hundreds of thousands of gees of centripetalacceleration while being subjected to high-pressure, high-velocity gasflows at temperatures often well above the melting points of commonmetals, and are required to do so for as many operating hours aspossible. Such an engineering feat can only be accomplished through useof exotic metallurgy and materials technologies, intricate film coolingtechniques, exacting structural design and testing, active enginemanagement, rigorous inspection and maintenance schedules, etc. All thisis made necessary by the pursuit of higher engine thermal efficienciesin light of existing energy loss mechanisms in the compressor andturbine.

It is true that an ‘ideal’ gas turbine engine having zero losses in itsturbomachinery components would still experience increased turbineintake temperatures in the course of achieving higher engine thermalefficiencies, since the required higher cycle pressure ratios woulddictate a larger temperature rise across its compression section. It canbe demonstrated, however, that such an ideal engine has little need tomaintain a large temperature rise across its heat addition section andcan therefore achieve much higher engine thermal efficiencies than thoseachieved by today's real-world gas turbines at a given turbine intaketemperature. Although an ideal engine is impossible to build, largereductions in turbomachinery component losses can translate into verylarge gains in engine efficiency before turbine intake temperaturesagain become a serious issue.

The Brayton cycle engine also provides an example of the operationalconstraints associated with flow-pressure coupling in turbomachines. Aspreviously detailed, Brayton cycle thermal efficiency is a function ofthe total pressure rise across the compressor and total drop across theturbine. Also as previously detailed, fixed blade orientations andconverging/diverging flow passages mean that quantities of compressorpressure rise & turbine pressure drop to be dependent on theirrespective flow rates. Furthermore, it can be understood that anengine's flow rate is generally linked to its power setting, since moregas flow is needed to absorb greater thermal power input if peak cycletemperature is to remain constant. Together these facts result inturbine engine thermal efficiency being dependent on engine powersetting. Such a power-efficiency coupling is a deal-breaker for manywould-be applications of this engine type, which is why so many modernair vehicles are powered by gas turbines while almost all modern groundvehicles are still powered by reciprocating engines. Air vehicle enginesspend most of their running time at or near their maximum power output,a very efficient mode for a gas turbine. Ground vehicle enginestypically spend most of their running time at a setting well below theirmaximum output, a mode in which a gas turbine cannot operate near peakefficiency.

Beyond Brayton cycle engines, all other end uses of turbomachines areimpacted in some way by velocity-dependent energy loss mechanisms and byflow-pressure coupling. The diminished efficiencies and constrainedoperational envelopes that result can be tolerable shortcomings or majorobstacles depending on the specifics of the end use in question. Ingeneral, any new technology that manages to solve these two fundamentalproblems would substantially improve the capabilities of turbomachinesand dramatically expand their real-world use.

2.3) Barriers to Improvement

-   -   2.3.1—Advantages of Centripetal Acceleration

A reasonable way to address velocity-dependent energy loss andflow-pressure coupling might be to eliminate their root cause: use ofconverging or diverging flow passages. Perhaps a machine can be devisedthat instead relies completely on the other available method forgenerating fluid pressure change: rotating radial flow passages.

(FIGS. 2A through 3A) In contrast to a converging 101 or diverging 102flow passage, which generates fluid pressure change through linearacceleration or deceleration of flow, a rotating radial flow passage 103subjects fluid to centripetal acceleration while directing flow towardor away from the axis of rotation. The centripetal acceleration createsa radial gradient of fluid pressure, locating higher pressures at outerradii 118 and lower pressures at inner radii 117. Fluid flowing radiallyoutward 104 through this gradient will be subject to pressure rise,while fluid flowing inward will be subject to pressure drop. Wherecentripetal acceleration is the sole mechanism of fluid pressure change,the severity of the pressure gradient is a function of rotationalvelocity only and is unaffected by the flow velocities relative topassage walls. This is a critical distinction: rotating radial flowpassages can produce significant pressure rise or drop without resortingto high flow velocities and associated high fluid shear rates atfluid-solid interfaces. And these flow passages can reliably producethat same pressure rise or drop regardless of variations in fluid flowrate through the passage, because the fluid motion that determinespressure change (tangential) is largely perpendicular to the fluidmotion that is determined by fluid flow rate (radial). It would seemthat rotating radial flow passages could theoretically provide asolution to both velocity-dependent energy loss and flow-pressurecoupling.

-   -   2.3.2—The Problem with Centrifugal Machines

(FIGS. 3A through 3C) Unfortunately, the advantages of this type of flowpassage are not fully leveraged. Existing centrifugal compressors andturbines generate less than half of their total fluid pressure rise/dropwithin rotating radial flow passages 103. As previously mentioned,impeller rotation causes flow vector deviation 131 where fluid enters117 and leaves 118 the impeller of any centrifugal turbomachine, soconverging/diverging flow passages 119 must be used at those locations.Those flow passages generate the remainder of the machine's pressurerise or drop. This is referred to as the impeller entry and exit problemin this specification. A closer look at this type of turbomachine willexplain it.

(FIGS. 3A through 3C) A typical single-stage centrifugal compressor orturbine consists of a single radial-flow impeller 116 enclosed within acasing. The impeller is a solid disc or disc-like structure to which anaxisymmetric set of blades 132 are attached. The blades run from theimpeller's hub 117 out to its rim 118 in a generally radial direction.The casing is shaped to provide a close-fitting shroud over the freeedges 133 of the blade set so as to limit fluid leakage past thoseedges. The empty spaces 103 between each adjacent pair of blades andbetween impeller disc and casing are the rotating radial flow passages.In a centrifugal compressor, fluid enters the impeller 117 near the hub,flows radially outward 104 through the impeller from lower to higherpressures, and exits 118 at the outer rim. The energy needed for fluidcompression comes from the consumption of shaft power by the impeller.In a centrifugal turbine, fluid enters the impeller at the outer rim,flows radially inward from higher to lower pressures, and exits at thehub. The energy liberated by fluid expansion is used to produce shaftpower. Since the impeller is a single solid object that rotates withuniform angular velocity, fluid near its outer rim has a great deal ofkinetic energy. In fact, about half of the energy that is transferredfrom impeller to fluid (compressor) or from fluid to impeller (turbine)takes the form of fluid kinetic energy associated with the hightangential velocities 134 at the rim.

(FIGS. 3A through 3C) This large kinetic energy fraction at the outerrim is the primary cause of the impeller entry and exit problem. In acentrifugal compressor, fluid at the rim 118 is leaving the impeller andentering stationary diffuser vanes 135 that surround the rim, which slowit down. Vector addition 131 at the rotating/stationary interfacetranslates the high fluid tangential velocities 134 at the rim into highflow velocities 136 entering the diffuser vanes, and the diverging flowpassages there 119 must convert that large fluid kinetic energy fraction(half of the total energy exchanged in the machine) into fluid pressure.In a centrifugal turbine, fluid at the rim is entering the impellerafter having been brought up to that same high tangential velocity byaccelerating through the stationary converging flow passages around theimpeller rim, so the large fluid kinetic energy fraction at the outerrim is produced by the pressure drop across these converging passages.In both of these cases, the stationary converging or diverging flowpassages 119 that surround the impeller's outer rim are responsible forabout half of the fluid pressure rise or drop across the device. Thereader should note that although the drawings show a typical centrifugalcompressor, a turbine would have more or less the same appearance, themajor differences between compressor and turbine being the direction offlow 104 through the device and the direction of the impeller's rotation137.

(FIGS. 3A through 3C) The secondary cause of the impeller entry and exitproblem is the kinetic energy fraction at the hub. At the impeller hub117, fluid flow must also enter (compressor) or exit (turbine) theimpeller blades 132. The fluid upstream of the compressor impeller entry138, or downstream of the turbine impeller exit, is assumed not to berotating. This is another rotating/stationary flow interface thatinvolves vector addition 131 and so requires converging or divergingflow passages. At the hub these passages 119 are located between theimpeller blades where the blades curl over from a radial directiontoward a tangential one. In a compressor, fluid flow entering theimpeller 138 first passes the blade leading edges 139 and then entersdiverging flow passages 119, which act to slow the entry flow velocity140 that resulted from the vector addition 131. In a turbine, fluidflowing toward the impeller exit passes through converging flow passages(the compressor's diverging passages in reverse) through which the fluidaccelerates in a tangential direction before passing the blade trailingedges, that tangential velocity opposing and canceling the impeller'srotational motion via vector addition. Again in both cases, fluidtangential kinetic energy due to the impeller's rotation is convertedinto, or from, fluid pressure by converging or diverging flow passages.Impeller tangential velocities 141 are lower near the hub radius, so thekinetic energy fraction there is significantly smaller than the fractionat the outer rim.

Together, the respective kinetic energy fractions at impeller hub andouter rim add up to well over half of the total amount of energy that isexchanged between centrifugal impeller and fluid. Well over half of theuseful output of a centrifugal compressor or turbine is produced withinconverging or diverging flow passages, and is therefore subject to thesame velocity-dependent energy loss and flow-pressure coupling thatplague axial-flow machines. A solution to the impeller entry and exitproblem is needed, because the advantages of rotating radial flowpassages cannot be fully realized if those passages do less than halfthe total work.

2.4) Critical Features of Improved Technology

To reduce or eliminate velocity-dependent loss and flow-pressurecoupling, turbomachines must use rotating radial flow passages only togenerate fluid pressure rise or drop. This cannot be done with currentradial-flow technology due to the impeller entry and exit problem. Somemeans must be found to exploit the benefits of radial-flow impellerswithout suffering the associated drawbacks. Use of centripetalacceleration must be retained, but established centripetal methods mustbe improved upon.

To that end, a new architecture for radial-flow turbomachinery isneeded. To fully exploit the advantages of centripetal fluid pressuregradients, it must be capable of transitioning fluid to and from highrotational speeds in a manner that minimizes fluid shearing rates at allfluid-solid interfaces and does not use converging or diverging flowpassages to handle any significant fluid energy quantities. The presentinvention seeks to achieve these goals, to lay a foundation forturbomachines that operate at significantly higher isentropicefficiencies and with enormously increased tolerance to variations inflow rate, even to the point of complete flow reversal.

3.) SUMMARY OF THE INVENTION

To generate fluid pressure rise or drop using only rotating radial flowpassages, the new architecture provided by the present invention mustrely on radial-flow impellers, and must therefore provide a solution tothe impeller entry and exit problem.

The solution is radial-flow fluid vortices.

A radial-flow fluid vortex is a mass of fluid that is rotating about anaxis line while generally moving toward or away from that line. A fluidvortex that contains radial mass transfer will tend toward havinguniform angular momentum. Where fluid angular momentum is uniform, fluidtangential velocity is inversely proportional to fluid radius. Thisinverse speed-radius relationship is the key to the solution.

(FIGS. 7B and 7C) Consider a hypothetical radial-flow impeller 142 thatis rotating slowly and is handling a radially outward fluid flow 143that is being discharged at its outer rim. The flow at the impeller exitis re-directed axially 144 around the rim edge 145 to the backside ofthe impeller disc 146, which has no blades or other means of exchangingtorque with the flow. At the backside this flow is directed radiallyinward, creating a fluid vortex that is co-axial to the impeller, inwhich fluid rotational speeds rise (147 vs. 148) as fluid flows radiallyinward. At some inner radius the fluid flow is again re-directed axiallyaround a corner, this time to enter the hub of a second radial-flowimpeller (not shown). The second impeller is co-axial to, and axiallyspaced from, the first impeller and is also rotating faster than thefirst. No converging or diverging flow passages are used to manipulatefluid tangential velocities between the two impellers. No vectoraddition is in play at impeller entries and exits. The transition offluid rotational speeds is accomplished using radial flow and conservedangular momentum.

After flowing outward through the second impeller, the fluid can thenturn to flow inward through a second fluid vortex on the backside of thesecond impeller, and then turn again into a third impeller and so on.Each subsequent impeller along the flow path spins faster and faster,until the fluid that started at a relatively slow rotational speed istraversing a high-speed impeller and is subject to the associated steepcentripetal fluid pressure gradients.

(FIG. 8B) Consider also a second hypothetical radial-flow impeller 149that is rotating at high speed and is handling a radially outward fluidflow 150 that is being discharged at its outer rim. Here, fluid leavingthe impeller continues radially outward through a bladeless flow region151, creating a fluid vortex in which fluid rotational speeds drop (152vs. 153) as fluid flows radially outward. At some outer radius the flowenters the hub of a second, much larger radial-flow impeller (notshown). The second impeller encircles the first impeller and is alsorotating more slowly than the first. Again as before, the transition offluid rotational speed between the first and second impellers isaccomplished using radial flow and conserved angular momentum.

Why is this second scenario important? Because a larger pressure risecan be generated across an outward-flow impeller-vortex-impellersequence than can be generated across a single, large outward-flowimpeller of the same overall diameter.

In both scenarios, the fluid flows through a vortex before or afterflowing through each impeller. Whereas existing turbomachines generallydirect working fluid through an alternating pattern of rotating andstationary blade sets, the present invention directs working fluidthrough an alternating pattern of blade sets and fluid vortices. Eachblade set represents an angular velocity ‘step’ and each fluid vortexrepresents a transition between ‘steps’.

The sequences outlined in both scenarios above are completelyreversible. Fluid that has left a high-speed impeller can come back toslow rotation by flowing through an outward-flow vortex, then a slowerinward-flow impeller, then an outward-flow vortex, and so on. Fluid canbe directed through a large centripetal fluid pressure drop by flowingthrough an inward-flow impeller, then an inward-flow vortex, then afaster inward-flow impeller, and so on.

These two reversed sequences, plus the two original scenarios, performfour basic operations: fluid spin-up, outward radial displacement tobuild pressure, inward radial displacement to lose pressure, and fluidspin-down. These four operations together make up the entire inventionand each of its embodiments. All are based on various combinations ofimpellers and fluid vortices.

This specification provides three primary embodiments along withsecondary variations on each. The first primary embodiment provides amachine consisting of two symmetrical halves: a compressor half and aturbine half, in which each impeller that adds energy to the compressorflow is powered by its symmetrical counterpart which is extractingenergy from the turbine flow. The second primary embodiment provides acompressor in which one impeller receives external shaft power input, oralternately a turbine in which one impeller produces net shaft power asthe machine's output. All other impellers in the second primaryembodiment power each other. The third primary embodiment, like thefirst, provides a machine having symmetrical compressor and turbinehalves. In the third embodiment, centripetal fluid pressure rise or dropis generated in stages across multiple inward and outward radialdisplacements at high rotational speeds, instead of across a singlehigh-speed radial displacement as is done in the first and secondembodiments. The third primary embodiment could also be capable ofsingle-shaft power input/output if provided with a mechanical gearingsystem to transfer shaft power between two of its rotors.

Since angular velocity stepping can only claim to transition fluidbetween low and high speed rotation, not between zero and high speedrotation, supplementary devices called angular velocity regulators aredisclosed and their role in transitioning fluid between zero and lowspeed rotation is discussed. In addition, the adverse effects ofpressure-driven fluid leakage between rotors and of conductive heattransfer through rotors are considered, as are methods for mitigation.Failure containment, noise and bearings are discussed. Finally, possibleend uses of angular velocity stepping are listed, including end usesthat may be currently impractical with existing technologies.

4.) BRIEF DESCRIPTION OF THE DRAWINGS

NOTES: (1) In all drawings that show arrows indicating working fluidflow (excluding FIGS. 1A thru 4, FIGS. 34A-B, 41A-B, and 43) arrowdirections may be considered reversible, consistent with the presentinvention's bi-directional flow capability. (2) In all cross-sectiondrawings, light gray shading indicates a blade surface.

FIG. 1A (Prior Art) is a perspective view of a simplified gas turbineengine with casing opened, showing compressor at left and turbine atright.

FIG. 1B (Prior Art) is a plan view of the compressor blades of FIG. 1A

FIG. 1C (Prior Art) is a plan view of the turbine blades of FIG. 1A.

FIG. 2A (Prior Art) is a close-up plan view of the compressor blades ofFIG. 1A and the flow vectors between rotating and stationary blade rows,showing the vector addition caused by blade rotation.

FIG. 2B (Prior Art) is a close-up plan view of the turbine blades ofFIG. 1A and the flow vectors between rotating and stationary blade rows,showing the vector addition caused by blade rotation.

FIG. 3A (Prior Art) is a perspective view of a typical centrifugalcompressor minus its casing, showing a rotating impeller surrounded by astationary diffuser.

FIG. 3B (Prior Art) is a close-up view of the flow vectors entering theleading edges of the impeller blades, showing the vector addition causedby blade rotation.

FIG. 3C (Prior Art) is a close-up view of the flow vector transitionbetween impeller blade trailing edges and diffuser blade leading edges,showing the vector addition caused by blade rotation.

FIG. 4 (Prior Art) is an enlarged diagram of the vector addition thatdetermines relative flow approach angle into a row of blades, showingthe effect of flow rate variations on approach angle.

FIG. 5A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow though the impeller of FIG. 5B

FIG. 5B is a perspective view of an outward-flowing impeller with flatradial blades.

FIG. 5C is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the impeller of FIG. 5B.

FIG. 6A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the fluid vortex of FIG. 6B.

FIG. 6B is a vector field representing steady inward radial flow througha fluid vortex of uniform angular momentum.

FIG. 6C is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the fluid vortex of FIG. 6B.

FIG. 7A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the impeller and vortex of FIGS. 7B &7C.

FIG. 7B is a perspective view of an outward-flowing impeller with flatradial blades that re-directs exiting flow at its rim around toward itsunderside.

FIG. 7C is a perspective view of the bladeless underside of the impellerof FIG. 7B, showing fluid from its topside entering at the rim into aninward-flowing fluid vortex.

FIG. 7D is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the impeller and vortex of FIGS. 7B &7C.

FIG. 8A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the impeller and vortex of FIG. 8B.

FIG. 8B is a perspective view of an outward-flowing impeller dischargingfluid into an outward-flowing fluid vortex.

FIG. 8C is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the two-part flow system of FIG. 8B.

FIG. 9A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the assembly of FIG. 9B.

FIG. 9B is a cross-section of an assembly that provides a flow paththrough an alternating sequence of outward-flowing impellers andinward-flowing fluid vortices.

FIG. 9C is an exploded perspective view of the assembly of FIG. 9B.

FIG. 10A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the assembly of FIG. 10B.

FIG. 10B is a cross-section of an assembly that provides a flow paththrough an alternating sequence of outward-flowing impellers andoutward-flowing fluid vortices.

FIG. 10C is an exploded perspective view of the assembly of FIG. 10B.

FIG. 11A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the compressor half of the firstprimary embodiment of the present invention.

FIG. 11B is a cross-section of the first primary embodiment of thepresent invention, showing five independent rotating structures and acasing.

FIG. 12 is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the compressor half of the firstprimary embodiment of the present invention.

FIG. 13A is a cross-section of the casing of the first primaryembodiment.

FIG. 13B is an exploded perspective view of the casing of FIG. 13A.

FIG. 14A is a cross-section of the rotating structure of the outermostand slowest impellers of the first primary embodiment.

FIG. 14B is an exploded perspective view of the rotating structure ofFIG. 14A.

FIG. 15A is a cross-section of the rotating structure of thesecond-slowest impellers of the first primary embodiment.

FIG. 15B is an exploded perspective view of the rotating structure ofFIG. 15A.

FIG. 16A is a cross-section of the rotating structure of the mid-speedimpellers of the first primary embodiment.

FIG. 16B is an exploded perspective view of the rotating structure ofFIG. 16A.

FIG. 17A is a cross-section of the rotating structure of thesecond-fastest impellers of the first primary embodiment.

FIG. 17B is an exploded perspective view of the rotating structure ofFIG. 17A.

FIG. 18A is a cross-section of the rotating structure of the fastest andinnermost impellers of the first primary embodiment.

FIG. 18B is an exploded perspective view of the rotating structure ofFIG. 18A.

FIG. 19A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the second primary embodiment of thepresent invention.

FIG. 19B is a cross-section of the second primary embodiment of thepresent invention, showing three independent rotating structures and acasing.

FIG. 20 is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the second primary embodiment of thepresent invention.

FIG. 21A is a cross-section of the casing of the second primaryembodiment.

FIG. 21B is an exploded perspective view of the casing of FIG. 21A.

FIG. 22A is a cross-section of the rotating structure of the low-speedouter impellers of the second primary embodiment.

FIG. 22B is an exploded perspective view of the rotating structure ofFIG. 22A.

FIG. 23A is a cross-section of the freewheeling mid-speed rotatingstructure of the second primary embodiment.

FIG. 23B is an exploded perspective view of the rotating structure ofFIG. 23A.

FIG. 24A is a cross-section of the input/output shaft and rotatingstructure of the high-speed inner impeller of the second primaryembodiment.

FIG. 24B is an exploded perspective view of the shaft and rotatingstructure of FIG. 24A.

FIG. 25A is a polar coordinate plot of fluid angular velocity vs. fluidradius representing flow through the compressor half of the thirdprimary embodiment of the present invention.

FIG. 25B is a cross-section of the third primary embodiment of thepresent invention, showing three independent rotating structures and acasing.

FIG. 26 is a dual plot of fluid kinetic energy and enthalpy vs. fluidradius representing flow through the compressor half of the thirdprimary embodiment of the present invention.

FIG. 27A is a cross-section of the casing of the third primaryembodiment of the present invention.

FIG. 27B is an exploded perspective view of the casing of FIG. 27A.

FIG. 28A is a cross-section of the rotating structure of the low-speedouter impellers of the third primary embodiment.

FIG. 28B is an exploded perspective view of the rotating structure ofFIG. 28A.

FIG. 29A is a cross-section of the freewheeling mid-speed rotatingstructure of the third primary embodiment.

FIG. 29B is an exploded perspective view of the rotating structure ofFIG. 29A.

FIG. 30A is a cross-section of the rotating structure of the high-speedinner impellers of the third primary embodiment.

FIG. 30B is an exploded perspective view of the rotating structure ofFIG. 30A.

FIG. 31A is a typical thermodynamic plot of gas pressure vs. gas volumefor a typical adiabatic compression or expansion.

FIG. 31B is a perspective view of a 3D plot of pressure vs. volume vs.time representing flow through the compressor half of the first primaryembodiment.

FIG. 31C is a perspective view of a 3D plot of pressure vs. volume vs.time representing flow through the second primary embodiment.

FIG. 31D is a perspective view of a 3D plot of pressure vs. volume vs.time representing flow through the compressor half of the third primaryembodiment.

FIG. 32 is a perspective view of a 3D projection of the relativerotational speeds of impellers and fluid vortices along a flow path.

FIG. 33A is a cross-section of a high-speed impeller with shroudedblades.

FIG. 33B is a cross-section of the impeller of FIG. 33A without a bladeshroud.

FIG. 34A is a typical flow passage within a typical impeller, showingthe tangential gradients of flow velocity that are imposed on inward oroutward radial flows by the coriolis acceleration.

FIG. 34B is the flow passage of FIG. 34A, showing the equivalentcoriolis secondary flow and resultant fluid ‘slip’ vectors at bothradial exits.

FIG. 35A is a schematic view of the impellers of the second primaryembodiment, showing outward radial spread.

FIG. 35B is the impellers of FIG. 35A, showing inward radial spread.

FIG. 36 is a cross-section of a variation of the first primaryembodiment in which one half is radially enlarged over the other half.

FIG. 37 is a cross-section of a two-stage variation of the secondprimary embodiment.

FIG. 38A is a cut-away perspective view of a valving system for thetwo-stage variation of the second primary embodiment, that valvingsystem set for parallel flow through the two stages.

FIG. 38B is the valving system of FIG. 38A, set for series flow throughthe two stages.

FIG. 39 is a cross-section of an assembly similar to that of FIG. 9B,here configured to prevent low fluid pressures at the inner radii of thefaster impellers.

FIG. 40 is a cross-section of a pre-pressurizing variation of the firstprimary embodiment, which has no inner-radii fluid vortices.

FIG. 41A is a perspective view of several vanes of an angular velocityregulator, showing regulating force and opposing fluid pressure beingapplied to each vane.

FIG. 41B is the regulator vanes of FIG. 41A, under reversed flowconditions.

FIG. 42 is a perspective view of a common system for applying regulatingforce to both angular velocity regulators of the second primaryembodiment.

FIG. 43 is a cross-section of the mid-radius area of the first primaryembodiment, showing paths of pressure-driven fluid leakage betweenrotating structures.

FIG. 44A is a cross-section of the hub area of the first primaryembodiment, using the rotor-on-axle bearing configuration.

FIG. 44B shows the hub area of FIG. 44A, using the rotor-on-rotorbearing configuration.

5.) GLOSSARY OF TERMS

Radial-Flow Impeller: A rotating component consisting of an axisymmetricset of blades that are attached to one or more solid discs or similarstructures, the blades shaped to guide a flow of fluid in asubstantially radial direction while exchanging torque, and thereforepower, with that flow, the disc or discs securing the blades againstcentrifugal forces and transferring shaft power to or from the blades.In the present invention, impeller blades can be straight and radial, orcan be oriented at some angle from the radial direction when viewing thedisc face-on. Straight radial blades offer complete flow-pressurede-coupling, while angled blades retain some degree of coupling whichmay be advantageous for certain end uses. Impeller blades in the presentinvention have leading and trailing edges that are generally, but notnecessarily, parallel to the rotational axis. Radial-flow impellerstransfer energy from rotor to fluid during outward radial flow, andtransfer energy from fluid to rotor during inward radial flow. Energylost or gained by the fluid consists of two equal parts: rotationalkinetic energy which varies with fluid tangential velocity as flow movesradially at semi-constant angular velocity, and enthalpy which varieswith fluid pressure as flow moves radially through a centripetalpressure gradient.

Impeller Power: The rate at which energy is consumed by a compressorimpeller or produced by a turbine impeller. For radial-flow impellerswith straight radial blades, assuming the fluid's angular velocityequals that of the impeller as it enters the impeller, neglecting slipor viscosity:

impeller power=(fluid mass flow rate)×(blade angular velocity)²×((bladeouter edge radius)²−(blade inner edge radius)²)

For blades that are angled to the radial direction, impeller powercalculations are more complicated.

Process Impeller: The highest-speed impeller(s) and the one(s)performing the bulk of the fluid compression and expansion processes. Incompressors, the process impellers are always outward-flow. In turbines,the process impellers are always inward-flow.

Spin-Up Impeller: Any impeller that transitions fluid from the lowrotational speeds at machine intake to the high-speed process impeller.Spin-up impellers are always outward-flow.

Spin-Down Impeller: Any impeller that transitions fluid from thehigh-speed process impeller back to the low rotational speeds at machineexhaust. Spin-down impellers are always inward-flow.

Bladeless Annular Volume: A ring-shaped volume encircling the commonrotational axis, which contains fluid that is rotating about that axisand is also flowing radially inward or outward. This volume is containedaxially between rotating structures or between casing sections and iscontained radially between upstream impeller blade trailing edges anddownstream impeller blade leading edges. This volume contains no bladesor other structures that would apply torque to the fluid, neglectingwall friction. The radial fluid flow within this volume forms a fluidvortex. The radial spacing between upstream impeller blade trailingedges and downstream impeller blade leading edges is defined as thatwhich is sufficient to allow fluid that is leaving the upstream impellerat some initial angular velocity to speed up or slow down to some fasteror slower angular velocity in the course of reaching the downstreamimpeller, due to partial or complete conservation of fluid angularmomentum across the radial spacing.

Radial-Flow Fluid Vortex: The fluid structure contained within thebladeless annular volumes in the present invention. A fluid vortex is amass of fluid that is rotating about an axis line, typically in theabsence of external torque once rotation has started. A radial-flowfluid vortex is a mass of fluid that is rotating about an axis linewhile generally moving toward or away from that line. A fluid vortexthat contains radial mass transfer will tend toward uniform angularmomentum (a free vortex), neglecting fluid viscosity. Where fluidangular momentum is uniform, fluid tangential velocity is inverselyproportional to fluid radius. In the present invention, fluid vorticesform where rotating fluid is made to flow in a radial direction througha bladeless annular volume. These vortices have the same rotational axisand spin direction as the impellers, and are used to speed up or slowdown fluid rotation between upstream and downstream impellers ofdifferent speeds. Total fluid energy is conserved across each vortex.During outward radial flow, fluid tangential velocity drops and fluidpressure rises as rotational kinetic energy is converted into enthalpy(pressure energy). During inward radial flow, fluid tangential velocityrises and fluid pressure drops as enthalpy is converted into rotationalkinetic energy.

Vortex Exit/Entry Spin Ratio: The ratio of the respective fluid angularvelocities at exit from, and entry to, a radial-flow fluid vortex.Equals the ratio of speeds of the two impellers that are immediatelydownstream and upstream of the vortex, assuming no coriolis slip at theupstream impeller exit. Neglecting fluid viscosity, the ratio is:

(fluid angular velocity@ exit)/(fluid angular velocity@ entry)=((radius@entry)/(radius@ exit))²

Entry into a fluid vortex in the present invention occurs where flowpasses blade trailing edges to leave the upstream impeller. Vortex exitoccurs where flow passes blade leading edges to enter the downstreamimpeller. The vortex's entry/exit radius ratio (the square root of itsexit/entry spin ratio) is therefore equal to the ratio of upstreamimpeller trailing edge radius to downstream impeller leading edgeradius.

6.) DETAILED DESCRIPTION OF THE INVENTION

6.1) Features of the Basic Invention

-   -   6.1.1—Fundamental Elements

The present invention provides a turbomachinery architecture in whichworking fluid gains or loses pressure by flowing through a radial-flowimpeller, then a radial-flow fluid vortex, then another impeller,another vortex, and so on. All impellers and fluid vortices rotatearound a single axis and in a common direction. Each impeller rotates ata somewhat higher or lower speed than the impeller upstream of it. Eachfluid vortex transitions fluid from the rotational speed of the upstreamimpeller to the higher or lower speed of the downstream impeller. Thealternating sequence of impeller, vortex, impeller, etc. can transitionworking fluid to and from the high rotational speeds needed to producesubstantial centripetal pressure change. This architecture offerssignificantly higher isentropic efficiencies and a dramatically expandedoperational envelope, relative to existing technologies.

Within this specification, working fluid is generally assumed to becompressible. However, the present invention is intended to handleincompressible and compressible fluids alike. Any descriptions ofworking fluid as having compressible characteristics should not beinterpreted as a narrowing of the invention scope to exclude the use ofincompressible fluids.

All fluid compression and expansion processes in this specification areassumed to be adiabatic. This assumption is based on: (1) structuralseparation of hot and cold machine sections, (2) a reasonably high ratioof fluid mass flow rate to flow path surface area.

The impeller and the fluid vortex are the two fundamental buildingblocks of the present invention in all its embodiments. Every machineconfiguration that is proposed in this specification can be described asa flow path through an alternating series of impellers and fluidvortices. A thorough understanding of the present invention starts witha thorough understanding of these two fundamental elements.

(FIGS. 5A through 5C) A radial-flow impeller 154 consists of anaxisymmetric set of blades 155 that are attached to one or more soliddiscs 156 or similar structures, the blades guiding a flow of fluid 157in a substantially radial direction while exchanging torque andtherefore power with that flow, the disc or discs securing the bladesagainst centrifugal forces while transferring shaft power to or from theblades. Impeller blades can be straight and radial 158, or can beoriented at some angle from the radial direction when viewing the discface-on. Radial-flow impellers transfer energy from rotor to fluidduring outward radial flow 157, and transfer energy from fluid to rotorduring inward radial flow. Energy gained by the fluid during outwardradial flow, or lost during inward radial flow, consists of two equalparts: rotational kinetic energy 159 which varies with fluid tangentialvelocity 160 as flow moves radially at semi-constant angular velocity161, and enthalpy 162 which varies with fluid pressure as flow movesradially through a centripetal pressure gradient.

(FIG. 5B) The radial-flow impellers of the present invention aregenerally similar to impellers used in existing centrifugalturbomachinery, but have the following specific features: (1) flowpassages 163 between blades 155 do not typically have significantconvergence or divergence near impeller entry 164 or exit 165, and (2)blade leading 166 and trailing edges 167 are generally parallel to therotational axis but may use other orientations as well, perhaps to setup desirable three-dimensional flow effects, e.g. controlledre-circulation patterns within bladeless annular volumes.

Since all working fluid particles generally cross each threshold betweenimpellers and vortices at or near a single radius, physical propertiesof the working fluid will be substantially uniform at any given radialposition along the flow path, and can therefore be defined andreferenced as a function of radius. For this reason, all polar andCartesian coordinate plots of fluid properties in this document useradius as the independent variable.

(FIGS. 6A through 6C) A fluid vortex is a mass of fluid that is rotatingabout an axis line, typically in the absence of external torque (oncerotation has started). A radial-flow fluid vortex 168 is a mass of fluidthat is rotating about an axis line while generally moving toward oraway from that line. A fluid vortex that contains radial mass transferwill tend toward a uniform radial distribution of angular momentum (afree vortex), neglecting fluid viscosity. Where fluid angular momentumis uniform, fluid tangential velocity 169 is inversely proportional tofluid radius. Total fluid energy is conserved across a vortex. Duringoutward radial flow, fluid tangential velocity decreases and fluidpressure increases as rotational kinetic energy is converted intoenthalpy (energy of pressure and temperature). During inward radial flow170, fluid tangential velocity 169 increases and fluid pressuredecreases as enthalpy 171 is converted into rotational kinetic energy172.

Fluid vortices are common and well-understood flow structures. Theyoccur within the wakes of moving vehicles and anywhere that one mass offluid is sliding past another. They also occur where a slowly rotatingmass of fluid is converging on a drain or intake. Fluid vortices alsoform at the tips of aircraft wings, propeller blades, sails, canoe orkayak paddles, etc, as an inevitable consequence of producingaerodynamic or hydrodynamic lifting force. In weather, atmospheric fluidvortices exist as hurricanes, cyclones, tornados, etc. In all of theseexamples, the vortex exists within a larger fluid volume. In the presentinvention, vortices are contained in empty chambers and are enclosed byrotating or stationary structures. These chambers are referred to asbladeless annular volumes in this specification.

A bladeless annular volume is a ring-shaped volume encircling the commonrotational axis, which contains fluid that is rotating about that axisand is also flowing radially inward or outward. This volume is containedaxially between rotating structures or between casing sections, and iscontained radially between upstream impeller blade trailing edges anddownstream impeller blade leading edges. This volume contains no bladesor other structures that would apply torque to the fluid, neglectingwall friction. The radial spacing between upstream impeller bladetrailing edges and downstream impeller blade leading edges is defined asthat which is sufficient to allow fluid that is leaving the upstreamimpeller at some initial angular velocity to speed up or slow down tosome faster or slower angular velocity in the course of reaching thedownstream impeller, due to partial or complete conservation of fluidangular momentum across the radial spacing.

-   -   6.1.2—Basic Impeller-Vortex Combinations

Radial-flow impellers and radial-flow fluid vortices are paired intoflow paths in one of two arrangements: (1) direction of radial flowthrough each vortex is opposite that through each impeller, or (2)vortices and impellers all have the same radial flow direction. Botharrangements will be considered in turn.

(FIGS. 7A through 7D) Consider a single radial-flow impeller 142 that isrotating relatively slowly and is carrying a fluid flow 143 radiallyoutward from an entry point at its hub 173 to an exit point at its outerrim 145. During its trip through the impeller, the fluid gains kineticenergy 174 as it gains tangential velocity 175, and its enthalpyincreases 176 as its pressure builds across the centripetal pressuregradient. Once at the rim, the flow does not enter stationary diffuservanes as it would in existing devices, but rather is re-directed axially144 around the rim edge 145 to the backside 146 of the impeller disc. Abladeless annular volume is formed in the axial spacing between theimpeller backside and another adjacent disc-like structure. Once in thebladeless annular volume, the flow is directed radially inward whileretaining most or all of the angular momentum it possessed at theimpeller exit, creating a fluid vortex. Enthalpy 177 is converted intorotational kinetic energy 178 within this vortex, so fluid pressurestarts dropping and fluid tangential velocity 179 begins to rise (147vs. 148) as fluid flows radially inward from the impeller rim. At someinner radius of the bladeless annular volume the fluid flow is againre-directed axially around a corner, this time to enter the hub of asecond radial-flow impeller (not shown) and perhaps to repeat the entirecycle. The second impeller is co-axial to, and axially spaced from, thefirst impeller. The second impeller is also rotating faster than thefirst. As fluid flows radially inward through the bladeless annularvolume, angular momentum conservation causes the fluid to pick uprotational speed until it has reached the speed of, and can flowstraight into, the faster second impeller. No converging or divergingflow passages are used to manipulate fluid tangential velocities neareither impeller's entry or exit. No vector addition is in play atimpeller entries and exits. The transition of fluid rotational speeds isaccomplished using radial flow and conserved angular momentum.

After flowing outward through the second impeller, the fluid can thenturn again to flow inward through a second bladeless annular volume onthe backside of the second impeller, and then turn again into a thirdimpeller and so on. Each subsequent impeller along the flow path spinsfaster and faster, until the fluid that started at a relatively slowrotational speed is traversing a high-speed impeller and is subject tothe associated steep centripetal fluid pressure gradients.

(FIGS. 8A through 8C) Consider also a second scenario in which a singleradial-flow impeller 149 is rotating at high speed and is again carryinga fluid flow 150 radially outward from an entry point at its hub 180 toan exit point at its outer rim 181. Again, the fluid gains kineticenergy 182 and enthalpy 183 across the impeller. Instead of turning acorner to flow radially inward, fluid leaving the impeller rim continuesradially outward through a bladeless annular volume 151 while retainingmost or all of the angular momentum it possessed at the impeller exit,again creating a fluid vortex. Here fluid kinetic energy 184 isconverted into enthalpy 185, so fluid pressure starts rising and fluidtangential velocity 186 begins to drop (152 vs. 153) as fluid flowsradially outward from the impeller rim. At some radius outside the firstimpeller exit, the flow enters the hub of a second, much largerradial-flow impeller (not shown), perhaps to repeat the entire cycle.The second impeller encircles the first impeller, and is rotating moreslowly than the first. Again as before, the transition of fluidrotational speeds between the first and second impellers is accomplishedusing radial flow and conserved angular momentum.

Why is this second scenario important? Because the severity of acentripetal fluid pressure gradient is proportional to the square offluid tangential velocity. To maximize centripetal fluid pressure riseacross a given radial displacement, radial distribution of fluidtangential velocity must be maximized. A single radial-flow impellerprovides maximum stress-limited tangential velocity at its outer rim,but has slower tangential velocities at inner radii. In the secondscenario, fluid flow reaches a maximum stress-limited tangentialvelocity at the outer rim of a smaller impeller, then slows down acrossa fluid vortex and speeds back up to that same stress-limited tangentialvelocity at the outer rim of a larger, slower impeller (same tangentialvelocity at larger radius means slower RPM). An outward-flowimpeller-vortex-impeller sequence can therefore generate greater overallpressure rise than a single, large outward-flow impeller of the sameoverall diameter.

Some existing types of centrifugal turbomachine also use bladelessannular spaces that surround the impeller. These spaces help to slowdown and pressurize the fluid that has left the rim of a compressorimpeller, or help to speed up the fluid that is about to enter the rimof a turbine impeller. Their function is to transition fluid betweenrotating impeller and stationary casing, not between impeller andfaster/slower impeller

The sequences outlined in both scenarios above are completelyreversible. Fluid that has left a high-speed impeller can come back toslow rotation by flowing through an outward-flow vortex, then a slowerinward-flow impeller, then another outward-flow vortex, and so on. Fluidcan be directed through a large centripetal fluid pressure drop byflowing through an inward-flow impeller, then an inward-flow vortex,then a faster inward-flow impeller, and so on.

These two reversed sequences, plus the two original scenarios, performfour basic operations: fluid spin-up, fluid spin-down, outward radialdisplacement to build pressure, and inward radial displacement to losepressure. Impellers that are involved in the fluid spin-up and spin-downoperations are called spin-up impellers and spin-down impellers,respectively. Impellers that are involved in either of the two radialdisplacement operations are called process impellers. These fouroperations together make up the entire invention and each of itsembodiments. All are based on various alternating sequences of impellersand fluid vortices.

(FIGS. 9A through 9C) Throughout each of these four basic operations,rotational speeds of fluid and impellers are largely (or completely, inthe case of straight radial impeller blades) determined by the entry andexit radii of each bladeless annular volume and by the first impeller'sspeed. If a spin-up impeller 187 having straight radial blades 188carries fluid flow 189 from radius A to radius B at uniform angularvelocity 190, and if that fluid enters the impeller with tangentialvelocity T, it will exit the impeller at tangential velocity (T×(B/A)).If that fluid is then directed into a bladeless annular volume 191 fromradius B back to radius A, it will exit that volume at tangentialvelocity (T×(B/A)²). The term (B/A)² is the vortex exit/entry spin ratioof a radial-flow fluid vortex from radius B to radius A. This ratio isequal to: (1) the ratio of fluid angular velocity leaving the vortex tothat entering it, and (2) the ratio of downstream impeller speed toupstream impeller speed, if both have straight radial blades. Fluidrotational speed is stepped up if B is greater than A, and is steppeddown if B is less than A. The speed 192 of the second spin-up impeller193 equals the vortex exit/entry ratio of the first vortex 194multiplied by the speed 190 of the first spin-up impeller 187. In turn,the speed 195 of the third spin-up impeller 196 equals the vortexexit/entry ratio of the second vortex 197 multiplied by the speed 192 ofthe second spin-up impeller 193. Working fluid that flows throughmultiple impellers and vortices in series will essentially be sped up orslowed down in distinct steps of angular velocity, hence the title.

(FIGS. 10A through 10C) Blade leading and trailing edge radii determinefluid and impeller rotational speeds in the two radial displacementoperations as well. If a process impeller 198 having straight radialblades 199 carries flow 200 from radius A to radius B and fromtangential velocity T to (T×(B/A)), and if that flow then passes througha bladeless annular volume 201 from radius B to radius C, its tangentialvelocity changes from (T×(B/A)) to ((T×(B/A))×(B/C)) which simplifies to(T×(B²/(AC))). Note that if (CB)=(B/A), then (T×(B²/(AC)))=T. Since allradial flow is in one direction, either C>B>A and fluid is flowingoutward 200 from lower to higher pressure (compressor), or C<B<A andfluid is flowing inward from higher to lower pressure (turbine). Fluidtangential velocity increases from impeller entry 202 to exit 203, andthen decreases from vortex entry 203 to exit 204, or vice-versa. If theratio of impeller exit radius to entry radius equals the ratio of vortexexit radius to entry radius, the amount of fluid tangential velocityrise across the impeller will equal the amount of tangential velocitydrop across the vortex, or vice-versa. As before, the speed of eachsuccessive process impeller 198, 205, 206 equals the speed of theimmediate upstream process impeller multiplied by the intermediatevortex exit/entry spin ratio. Since a transit of each impeller-vortexpair involves both an increase and a decrease in fluid tangentialvelocity, the resultant tangential velocity distribution across severalelements can approximate a consistent value 207.

The reader should note that some degree of fluid shear must occur withina radial-flow fluid vortex due to its non-uniform distribution of fluidangular velocities. Fluid shear will generate some amount of viscousenergy loss in any real-world fluid. Although that loss need notappreciably impact machine efficiency, it will cause a minor flatteningof the radial gradient of fluid angular velocity within each vortex anda small adjustment of its exit/entry spin ratio toward unity. The exactamount of exit/entry spin ratio adjustment will be proportional to fluidviscosity and to severity of the radial gradient of fluid angularvelocity, and will likely be inversely proportional to fluid flow ratethrough the vortex. This effect must be taken into consideration whendesigning a velocity-stepping turbomachine.

-   -   6.1.3Rotating Structures, Impellers, and Blades

(FIGS. 11B, 16A, 16B, 19B, 22A, 22B, 25B, 28A and 28B) Embodiments ofthe present invention use one or more spin-up impellers to perform fluidspin-up, one or more process impellers to generate pressure rise ordrop, and one or more spin-down impellers on top of that to performfluid spin-down. This can add up. To keep the number of independentrotating structures (rotors) per machine to a minimum, multipleimpellers can be carried on each structure. The drawings show severalrotating structures 208, 209, 210 that include more than one impeller(per symmetrical half). Where two adjacent rotors are connected to eachother by more than one flow path, each fluid vortex between the two musthave an exit/entry spin ratio that equals the ratio of downstream rotorspeed to upstream rotor speed. If impeller B on rotor 1 is immediatelydownstream of impeller A on rotor 2, and impeller D on rotor 2 isimmediately downstream of impeller C on rotor 1, then the fluid vortexbetween impellers A and B must have the same exit/entry spin ratio asthe vortex between impellers C and D. If that is true, then the ratio ofimpeller B leading edge radius to impeller A trailing edge radius mustequal the ratio of impeller D leading edge radius to impeller C trailingedge radius. In this way design choices about impeller speeds andconfigurations of rotating structures determine radial proportions ofthe machine, or vice-versa.

Because working fluid is spun up by crossing one or more spin-upimpellers in series, and then spun down again by crossing one or moreadditional spin-down impellers, and because similar-speed impellersshould be joined together on common rotating structures, it turns outthat the most effective configuration in which to arrange the multiplerotating structures of a complete machine is to ‘nest’ them, one insideanother. The fastest and smallest structure is in the center and isenclosed by the second fastest, itself enclosed by the third fastest andso on out to the machine casing. Fluid spins up as it penetrates eachsuccessive ‘shell’ in turn until reaching the high-speed interior, andthen spins back down as it passes back through each shell to exit themachine.

(FIGS. 11B, 14A through 18B) Although it is generally true thatcompressors transfer energy from shafts to fluid flows and that turbinestransfer energy from fluid flows to shafts, the embodiments each containone or more impellers that reverse those energy flow trends. In thefirst primary embodiment, for example, spin-up impellers 211 and processimpellers 212, 213 in the compressor transfer energy from shaft tofluid, but spin-down impellers 214, 215, 216 in the compressor transferenergy from fluid to shaft (act as turbine impellers). In the samemanner, spin-down impellers 219 and process impellers 217, 218 in theturbine transfer energy from fluid to shaft, but spin-up impellers 220,221, 222 in the turbine transfer energy from shaft to fluid (act ascompressor impellers). This contrast of function becomes important forembodiments of the present invention that involve a turbine driving acompressor, where the normal flow of power from turbine side tocompressor side is reversed between some impellers.

-   -   6.1.4—Velocity-Dependent Loss & Flow-Pressure Coupling

The key elements of the present invention's solution to the impellerentry and exit problem are: (1) flow paths that cross multiplestaggered-speed impellers in series, and (2) radial-flow vortices thatspeed up or slow down fluid rotation between impellers. Workingtogether, these two elements take fluid from a resting state up tohigh-speed rotation and back to rest, without involving converging ordiverging passages, vector addition, or high fluid shearing rates alongflow surfaces.

The velocity-dependent losses that do exist within impellers are duelargely to flow velocities and to coriolis effects. Because flowvelocities are proportional to machine flow rate, and can be reduced ata given flow rate by use of flow passages with larger cross-sections,energy losses within blade sets are controllable and need notappreciably impact machine efficiency unless machine size is severelyconstrained for a given flow rate.

(FIG. 32) Losses are slightly larger within bladeless annular volumes223, where radial flow velocities 224 are accompanied by a mismatch ofangular velocities 225 between fluid and annular walls 226 due to thefact that rotating structures 227 have uniform angular velocities 228while radial-flow vortices do not. Respective angular velocities offluid and walls can be equal only at entrance 229 and exit radii 230 ofeach bladeless annular volume, and must be unequal at all other radiiwithin those volumes. The resulting fluid shearing rates at the annularwalls can be limited by reducing the vortex exit/entry spin ratios, andso also reducing the speed differences 231 between upstream anddownstream impellers and using more steps to achieve a given overallangular velocity maximum. Fluid shearing rates can also be reduced ifupstream rotor walls 227 meet downstream rotor walls 226 at some radialmidpoint in each bladeless annular volume 223. Doing so restricts fluidshear velocities on the annular walls to half or less of the totalrotational speed difference across the vortex. NOTE: the high-speedprocess impellers in the machine might not be able to extend rotor wallsoutside the tip radius of their outer blade edges due to centrifugalstress concerns.

Unlike energy loss mechanisms, certain types of flow-pressure couplingmay be advantageous for machines performing certain tasks. Therelationship between flow and pressure can be optimized or eliminatedaltogether, by modifying impeller blade shapes. Because vector additionand converging-diverging flow passages (as they apply to the existingtechnology) have been eliminated from the present invention, the onlyremaining design parameter that determines the degree of flow-pressurecoupling in a velocity-stepping turbomachine is the shape of theimpeller blades.

Impeller blades that are straight and aligned with the radial directionprovide complete flow-pressure de-coupling, because variations in flowrate have no effect on fluid tangential velocity distributions withinimpellers and vortices, and therefore have no effect on totalcentripetal fluid pressure rise or drop across the machine.

The importance of complete flow-pressure de-coupling is difficult tooverstate: fluid pumps and motors, heat engines, heat pumps, etc. canoperate at steady pressure differences or cycle pressure ratios whilehandling a very wide range of working fluid flow rates, and are evencapable of handling a complete reversal of flow direction altogether.Fluid pumps can operate under reversed flow to function as motors, andheat engines can be reversed to function as heat pumps (without changingtemperature distributions within the machine or within other cyclecomponents such as heat exchangers). This broad tolerance of variationin fluid flow rate and flow direction gives velocity-steppingturbomachines enormous utility and flexibility compared to existingtechnology, as no existing type of turbomachine can make these claims.

Impeller blades that are angled to the radial direction when viewing thedisc face-on will produce some degree of flow-pressure coupling, becausethe resultant flow velocities through such blades will have sometangential component. By manipulating the blade angle with respect tothe radial direction, the designer can control what kind offlow-pressure coupling is produced within impellers, if any is desired.This design feature could prove valuable for specific end uses.

The reader should note that if fluid enters an impeller with sometangential velocity component relative to that impeller, that tangentialcomponent must be factored in along with the exit/entry spin ratio ofthe upstream fluid vortex when calculating the speed ratio between thatimpeller and the immediate upstream impeller. If fluid leaves animpeller with some tangential velocity component relative to thatimpeller, that component must be factored in along with the exit/entryspin ratio of the downstream fluid vortex when calculating the speedratio between that impeller and the immediate downstream impeller. Sincetangential components of flow velocity vary with flow rate, impellerspeed ratios will also vary with flow rate.

-   -   6.1.5—Structural Considerations

If straight radial blades are used in a velocity-stepping turbomachine,they provide additional structural benefits to the present invention.Straight radial blades align their structure with the direction ofcentrifugal force application, so the blade material can carrycentrifugal loads as a combination of tensile and shearing internalstresses. Bending stresses in blades can be limited to those caused byfluid reaction loads, which are much smaller than centrifugal loadsunless blade rotational speed is low or fluid density is high. Wherebending stresses are a minor factor, blades can be made fairly thin andlightweight. Lightweight blades impose less centrifugal loading on theimpeller hubs or discs to which they attach, so those components canalso be smaller and lighter. The reader should note that the bendingstresses that do occur in blades are not only caused by the fluidreaction loads acting directly on blade surfaces but are also caused byshaft power transfer through rotating structures (fluid reaction loadsacting on other blades).

(FIGS. 33A and 33B) The previous statement that velocity-dependentlosses within impellers are due largely to flow velocities is based onthe assumption that all impeller flow passages are fully enclosed,meaning the blades 232 attach to a rotating structure on both sides ofthe flow path 233, 234, so that all flow surfaces within impeller flowpassages are rotating at impeller speed. This is in contrast to aconfiguration in which blades 235 are attached on one side only 236 andhave a free side 237, with the other end wall 238 being part of anadjacent rotating structure 239 that turns at a different speed. If thesecond end wall turns at a different speed, fluid shearing rates withinimpeller flow passages are increased.

In most sets it is essential that blades be attached to both walls toprovide mechanical attachment between rotating structures on both sidesof the flow path, and to carry shaft power between those structures. Thefastest process impeller in the machine, however, is generally astand-alone structure and therefore might not include a second end wall,for stress reasons. The high centrifugal loading that is imposed onhigh-speed impeller blades can be carried by the impeller hub. Howeverthat same loading acting on a second end wall, one that is rotating atimpeller speed and is essentially a disc with a large central hole,could subject it to unacceptably large circumferential stresses. Thesecond wall of the fastest blade set might therefore need to be part ofthe next slower rotor, with efficiency considerations taking a back seatto structural necessity.

-   -   6.1.6—Coriolis Effects

(FIG. 34A) The subject of coriolis effects must be considered in thisspecification. Any mass that rotates about an axis at constant angularvelocity while moving radially toward or away from that axis issubjected to a coriolis acceleration acting in the tangential directionthat equals twice the mass's angular velocity multiplied by its radialvelocity. The flows within each impeller of the present inventionexperience this situation, and are therefore subjected to the coriolisacceleration. In fact the reaction loading on the impeller blades 240resulting from this acceleration is the basis for how energy transferbetween shaft and fluid occurs within every impeller. As always, a fluidvolume responds to an applied acceleration by forming an internalpressure gradient that is aligned with the acceleration vector. In thiscase, the acceleration vector and the resultant pressure gradient areperpendicular to the direction of fluid flow through the impellers,resulting in a tangential gradient of flow velocity. Impeller flowpassages 241 in which fluid is moving away from the rotational axis willhave higher flow velocities 242 toward the spinward side of the passageand lower flow velocities 243 toward the anti-spinward side, whilepassages in which fluid is moving toward the rotational axis will havelower flow velocities to spinward 244 with higher velocities toanti-spinward 245. The tangential gradient of flow velocity isindependent of fluid flow rate: at sufficiently low flow rates the fluidon the slow side of the passage will reverse its radial flow direction.

(FIG. 34B) This pattern may be simply thought of as a coriolis-inducedsecondary flow: a fluid rotation 246 opposite the direction of impellerrotation 247 that is superimposed on the radial fluid motion within eachflow passage. The secondary flow creates an exit deviation: fluid flowexiting an impeller will ‘slip’ 248 to an angular velocity slightly lessthan that of the impeller if it is moving away from the rotational axisduring exit, or it will ‘slip’ 249 to an angular velocity slightlygreater than that of the impeller if it is moving toward the axis duringexit. The percentage slip that occurs is proportional to the bladespacing in the impeller. With regard to the present invention, thereader should note that the ratio of rotational speeds of a downstreamimpeller and an upstream impeller is determined not only by theintermediate vortex exit/entry spin ratio, but is also determined by theamount of coriolis slip that occurs as fluid exits the upstreamimpeller. Toward the goal of facilitating larger speed ratios betweenadjacent pairs of impellers, all flow sections in which outward radialflow turns around to become inward radial flow, or vice-versa, are shownas being contained within impeller blades and not within bladelessannular volumes. In placing each outward/inward radial flow switchbackwithin the blades of an impeller, a performance advantage might begained: coriolis slip that is added to vortex exit/entry spin ratiosinstead of being subtracted from them.

(FIGS. 16B, 22B, 28B) The reader should note that excessivecoriolis-induced secondary flows within impeller flow passages areundesirable, because very large tangential gradients of flow velocitycan create high fluid shearing rates at passage walls. The best way tocontrol these secondary flows is by increasing the number of blades perimpeller to decrease blade spacing, but blades that are too closelyspaced together present excessive solid surface areas to the flow,thereby magnifying losses caused by flow velocities. At a given overallflow rate, optimal blade spacing exists at the ideal trade-off betweenminimal secondary flow strength and minimal surface area. For impellers211, 219, 250, 251 that have large outer/inner radius ratios, achievingoptimal blade spacing may require the insertion of partial blades 252that extend from the impeller's outer radius to halfway to its innerradius. These partial blades reduce the large blade spacing at outerradii without creating unnecessarily close blade spacing at inner radii.

-   -   6.1.7—Materials

Material selection for fabrication of the present invention is informedby the operating conditions being imposed on machine components. Theprimary conditions of concern are (1) high centrifugal loading on movingparts resulting from high rotational speeds, and (2) possibletemperature extremes, both high and low, resulting from use of certainthermodynamic cycles or working fluids. For end uses that demand thelargest possible pressure change or ratio from a single machine, thefastest impellers in that machine must rotate at the highest possiblespeed allowed by material stress limits. For impellers and rotatingstructures that are subject to high centrifugal loads and tohigh-temperature fluids, material selection is well informed by the bestpractices used by manufacturers of gas turbine engines. Suitable choicesinclude stainless steels, alloys of titanium, nickel or cobalt, ceramiccomposites, etc. Where high centrifugal loads are experienced at coolertemperatures, the primary qualifying criteria is the ratio of materialstrength to density. Suitable choices include carbon, Kevlar or glassfiber composites and other composite materials. Some exotic carbon fibercomposites may be suitable for high temperatures. For impellers andrelated structures that rotate more slowly at cooler temperatures,cheaper materials such as aluminum alloys, steel, and even high-densityplastics are suitable. Components that are subjected to cryogenicenvironments should be fabricated from materials appropriate for use atthose temperatures, such as aluminum, copper, nickel, titanium and thealloys thereof, austenitic stainless steels, glass fiber composites,etc. Anticipated operating temperatures can generally determine materialselection for machine casings, as casing stresses are primarily afunction of internal fluid pressure distributions and need not be assevere as centrifugal stresses.

6.2) Variations on the Basic Invention

-   -   6.2.1—First of Three Primary Embodiments

(FIGS. 11A, 11B, 13A through 18B) Using various permutations of thealternating impeller-vortex flow path, and encompassing the four basicoperations, three primary embodiments are established here. The firstprimary embodiment is a compressor being driven by a turbine. Theturbine and compressor have a common rotational axis 253 and areessentially mirror images of each other across a plane of symmetry 254,creating two symmetrical halves of a complete machine. This embodimentis useful as a heat engine, heat pump, or other machine that performs athermodynamic cycle, or simply one that transfers energy from one fluidflow to another. The compressor half 255 of this embodiment (1) spins upworking fluid at inner radii through one or more outward-flow spin-upimpellers 211 and one or more inward-flow vortices 256, (2) generatescentripetal pressure rise through one or more outward-flow processimpellers 212, 213 and one or more outward-flow vortices 257, and (3)slows fluid rotation back down at outer radii through one or moreinward-flow spin-down impellers 214, 215, 216 and one or moreoutward-flow vortices 258. The turbine half 259 performs these exactsteps in reversed flow: spin-up at outer radii, pressure drop throughinward flow, and slow-down at inner radii. Every inward-flow impeller inone half of the machine powers its outward-flowing symmetricalcounterpart in the other half of the machine. Shaft power is transferredfrom the inner and mid-radii impellers of the turbine half to theirsymmetrical counterparts, and a smaller amount of energy is transferredin the other direction, from the outer-radii impellers of the compressorhalf to their symmetrical counterparts. Impellers are grouped by speedso that each group can be carried on a single rotating structure. Thesestructures span both symmetrical halves and provide the physical meansfor shaft power transfer between halves. Each rotating structure isenclosed within the next structure out, and each spins faster than theone enclosing it, with the outermost structure being enclosed by thecasing 260. The complete assembly shows 5 independent rotatingstructures 261, 262, 208, 263, 264, which each have their own drawingsheet. The quantity of total fluid pressure rise and drop that can beprovided by the first primary embodiment is limited by allowable machineouter diameter and by allowable rotor speeds.

(FIG. 12) Overlaid plots of fluid rotational kinetic energy vs. fluidradius and of enthalpy vs. fluid radius show the various energyexchanges that occur within the compressor half of the first primaryembodiment. In the plots, enthalpy and kinetic energy are shown toincrease or decrease in unison across each impeller (e.g. 265 & 266),and are shown as having opposite slopes across each vortex (267 & 268).Enthalpy shows an expected net increase across this adiabaticcompression, while kinetic energy is stepped up to the higher values atinner radii and is stepped back down at outer radii. The reader shouldnote that the intake enthalpy 269 is not the lowest 270 in the machine,and the exhaust enthalpy 271 is not the highest 272. These same plots,with flow arrows reversed, describe the adiabatic expansion in theturbine half.

-   -   6.2.2—Second Primary Embodiment

(FIGS. 19A, 19B, 21A through 24B) The second primary embodiment is acompressor in which one impeller receives external power input on ashaft, perhaps from an electric motor or other mechanical power source.The second primary embodiment is also a turbine in which one impellerproduces external power output on a shaft, perhaps to turn a generatoror otherwise act as a mechanical power source. All other impellers inthis embodiment must power (or be powered by) each other. Other thanthese features, the second primary embodiment functions in a mannersimilar to the first. When operating as a compressor, it: (1) spins upworking fluid at inner radii through one or more outward-flow spin-upimpellers 250 and one or more inward-flow vortices 273, (2) generatescentripetal pressure rise through one or more outward-flow processimpellers 274 and one or more outward-flow vortices 275, and (3) slowsfluid rotation back down at outer radii through one or more inward-flowspin-down impellers 276 and one or more outward-flow vortices 277. Whenoperating as a turbine, it performs these exact steps in reversed flow:spin-up at outer radii, pressure drop through inward flow, and slow-downat inner radii. The process impeller 274 is secured to the input/outputshaft 278. Each inward-flow spin-down impeller 276 that is downstream ofthe fastest impeller powers a dedicated outward-flow spin-up impeller250 that is upstream of the fastest. Each driven and driving pair ofimpellers is carried on an independent rotating structure. As before,each rotating structure is enclosed within the next structure out, andeach spins faster than the one enclosing it, with the outermoststructure being enclosed by the casing 279. The complete assembly shows3 independent rotating structures 209, 280, 281, which each have theirown drawing sheet. The quantity of total fluid pressure rise and dropthat can be provided by the second primary embodiment is limited by thespeed of the input/output shaft.

The input/output shaft is secured to the high-speed process impellerbecause that impeller is responsible for performing the compression orexpansion process. The spin-down impellers downstream of the processimpeller are used to recover some of the fluid kinetic energy thatleaves the process impeller and recycle that energy back into the flowvia the spin-up impellers. Any kinetic energy wastage is viewed as apercentage of the input/output shaft power in calculating overall energyefficiency.

Because all impellers other than the process impeller must power eachother, their configuration is constrained by the unique problem ofradial spread. Radial spread happens because: (1) impeller powers mustbe balanced between driven and driving impellers, and (2) all vorticesbetween two particular rotating structures must have the same exit/entryspin ratio. Impeller power (with straight radial blades) equals bladeouter edge radius squared minus blade inner edge radius squared,multiplied by the set's angular velocity squared and by its fluid massflow rate. Because each rotating structure has a uniform angularvelocity and because all impellers in the second primary embodimentexperience the same fluid mass flow rate, balancing of impeller powersbetween driven and driving impellers requires that one impeller's outerblade radius squared minus inner blade radius squared must equal that ofthe other impeller. For rotating structures having one impeller furtherfrom the rotational axis than the other, this means that the impellerfurther out must have a smaller leading-to-trailing-edge radial distancethan the impeller closer in. Meanwhile, fluid vortices further from therotational axis must cover a larger radial distance than vortices closerin if both are to have the same exit/entry spin ratio.

(FIGS. 35A and 35B) Now consider the basic architecture of the secondprimary embodiment: the high-speed process impeller 282 places itstrailing edges at some radial distance from its leading edges, and thetwo fluid vortices 283, 284 that separate it from the two second fastestimpellers add to that radial difference because both vortices must havethe same exit/entry spin ratio. The two second-fastest impellers 285,286 then further add to that radial distance because their powers mustbalance, and so forth to the next two fluid vortices 287, 288 and thethird-fastest impellers 289, 290, if they exist. This is radial spread,and it results in one of two machine geometries: (1) the flow path 291on one side of the process impeller gets further from the rotationalaxis 292 across every impeller-vortex pair, or (2) the flow path 293 onthe other side of the process impeller gets closer to the rotationalaxis 294 across every impeller-vortex pair. The drawings of the secondprimary embodiment show it as having that first radial spread geometryand therefore locating the process impeller at the machine's innerradii. The inventor chose to illustrate this option because it has afundamental energy efficiency advantage over the second spread geometry.In turn, the second radial spread geometry has an input/output torqueadvantage over the first, so both geometries can be viable options.

(FIG. 20) Plots of fluid kinetic energy and enthalpy for the secondprimary embodiment show that total enthalpy increase from inlet 295 tooutlet 296 is smaller relative to maximum impeller tip kinetic energy297, when compared to the first primary embodiment. As before, enthalpyand kinetic energy increase or decrease in unison across each impeller(e.g. 298 & 299), and have opposite slopes across each vortex (300 &301). As before, these same plots in reverse describe the adiabaticexpansion performed by the second primary embodiment when operating as aturbine.

-   -   6.2.3—Third Primary Embodiment

(FIGS. 25A, 25B, 27A through 30B) The third primary embodiment issimilar to the first in that it is a compressor being driven by aturbine, the turbine and compressor again having a common rotationalaxis 302 and being mirror images of one another across a plane ofsymmetry 303. Unlike the first and second primary embodiments, whichgenerate fluid pressure change across a single large radialdisplacement, the third primary embodiment generates fluid pressurechange as the net product of several consecutive radial displacements ofalternating directions. In the compressor half 304 of this embodiment,working fluid: (1) spins up through one or more outward-flow spin-upimpellers 305 and one or more inward-flow vortices 306, (2) crosses acentripetal pressure rise through one or more outward-flow processimpellers 307 and one or more outward-flow vortices 308, and then (3)crosses a smaller centripetal pressure drop through one or moreinward-flow spin-down impellers 309 and one or more inward-flow vortices310 to return to inner radii where it can repeat step 2 further down therotational axis. After enough cycles between steps 2 and 3, the fluidfinally slows down through one or more inward-flow spin-down impellers311 and possibly one or more outward-flow vortices (not shown). Theprocess impeller(s) involved in step 2 add a large amount of energy tothe flow, while the spin-down impeller(s) involved in step 3 take someof that energy back out. As before, the turbine half 312 performs theseexact steps in reversed flow. The linking of compressor to turbine toform a complete machine allows the low-power step 3 spin-down impellersof the compressor to drive those of the turbine, and allows thehigh-power step 2 process impellers of the turbine to drive those of thecompressor. Again, impellers are grouped by speed to be carried oncommon rotating structures that span both machine halves and providemeans for shaft power transfer. The drawings show 3 independent rotatingstructures 210, 313, 314 enclosed within a casing 315, each having itsown drawing sheet. Drawings of the third primary embodiment show onlythe compressor half of the assembly and each structure. The quantity oftotal fluid pressure rise and drop that can be provided by the thirdprimary embodiment is limited only by how many outward-and-inward radialcycles it can include. The drawings show an assembly having 3outward-and-inward radial cycles.

The large central radial displacements of the first and second primaryembodiments inevitably dictate a machine of larger relative diameter andsmaller relative axial length. The repeated radial cycling of the thirdprimary embodiment sets up a machine of smaller relative diameter andlarger relative axial length. This correlates with the typicalproportions of existing gas turbines, steam turbines and some otherturbomachines, so the third primary embodiment can serve as a drop-inreplacement for such equipment, able to fit into existing compartments,nacelles, buildings, etc.

The third primary embodiment might be adapted to be capable of powerinput/output on a single shaft, providing an alternative to the secondprimary embodiment. This would require the use of mechanical gears, suchas a planetary gear system, to exchange shaft power between the processimpellers and the outer radii impellers so as to eliminate the need forthe second symmetrical half of the machine.

(FIG. 26) Plots of fluid rotational kinetic energy and enthalpy for thethird primary embodiment illustrate its unique advantage: large enthalpyincrease from inlet 316 to outlet 317 for a given maximum impeller tipkinetic energy 318, thanks to repeated outward-and-inward radialcycling. The enthalpy plot shows 3 radial cycles consistent with thedepicted embodiment. As before, these plots with reversed flow arrowsdescribe the adiabatic expansion in the turbine half.

(FIGS. 31A through 31D) As previously mentioned, all fluid compressionand expansion processes in the present invention are assumed to beadiabatic, and likely appear as a standard adiabatic curve 319 ifdepicted on a standard pressure-volume plot. If plotted in threedimensions with time on the z-axis, however, the progression of fluidproperties through the first 320, second 321, and third primaryembodiments 322 are revealed as being somewhat meandering, showing atwo-steps-forward-one-step-back motion along the adiabatic curvewherever inward-and-outward radial cycling is needed within eachembodiment.

Consideration should be given to the dynamic restoring forces associatedwith impeller speed deviations that enable each rotating structure tomaintain a stable angular velocity. Suppose a given rotating structurewithin a velocity-stepping turbomachine is spinning at its design speedrelative to its neighboring structures and has balanced powers betweenits driving and driven impellers. If that structure were to slow downslightly for some reason, fluid flow at the leading edges of each of itsimpeller blades would be rotating slightly faster than those blades andwould impart a slight force on each blade in the direction of rotationas fluid rotation is slightly slowed upon entering each impeller. Theresult would be a slight reduction of impeller power in driven impellersand a slight increase of impeller power in driving impellers, and thatpower imbalance would act to speed up the structure. Similarly, a slightincrease in speed would create an impeller power imbalance that wouldact to slow the rotating structure.

-   -   6.2.4—Non-Symmetrical First and Third Primary Embodiments

(FIG. 36) Balancing of driving and driven impeller powers in the firstand third primary embodiments, with their two symmetrical halves,requires that fluid flow rates are equal for both halves and that noneof the rotating structures experience significant bearing friction, sealrubbing, or any other substantial drag. If either condition is not met,the first and third primary embodiments can be re-balanced if onemachine half is enlarged in the radial direction by some uniformpercentage over the other half. As previously stated, impeller power isproportional to (valid for all embodiments) blade outer radius squaredminus blade inner radius squared. If the respective radii 323 of allblade leading and trailing edges in one machine half are increased overtheir counterpart radii 324 in the other half by some uniform factor F,the impeller powers per unit fluid mass flow of all impellers in thatlarger half are multiplied by F². This radial enlarging of one machinehalf can be used to re-balance impeller powers if: (1) the two halvescarry unequal fluid mass flow rates, namely a flow rate in the smallerhalf that is F² times the flow rate in the larger half, or (2) a netdrag force on the rotating structures resulting from bearing friction,seal rubbing, or other drag mechanisms that brings total shaft powerconsumption to F² times the total shaft power production in asymmetrical machine. Although the drawing shows a non-symmetrical formof the first primary embodiment only, the concept applies to the thirdprimary embodiment in the same manner.

Unequal fluid mass flow rates can occur in the two halves of the firstor third primary embodiments if each half is handling its own distinctfluid stream, especially if the two streams are of different fluids.Unequal flow rates can also occur in a device performing a completethermodynamic cycle if substantial fluid mass flow is being added orremoved between compressor and turbine. This would be the case if cyclepower input/output were being provided by a fraction of the machine'sflow rate acting across the full cycle pressure ratio (e.g., compressorbleed power) instead of the more common full machine flow rate actingacross the exhaust-to-ambient pressure difference. This would provide anengine whose output is directly available in the form of high-pressureflow.

If a non-symmetrical form of the first or third primary embodiments isbeing used to compensate for bearing or seal friction or some otherdrag, power lost in each structure should be small percentage of totalshaft power being transmitted. If so, the radial scaling factor F of onemachine half over the other can be very close to one, that is, thelarger half need only be slightly larger than the smaller half. NOTE:compensating for bearing or seal friction in this manner will work inone flow direction only. If flow is reversed, non-symmetrical impellerpower imbalance adds to frictional power loss instead of subtractingfrom it.

-   -   6.2.5—Multi-Staging

As is frequently done with existing technology, velocity-steppingturbomachines can be multi-staged: multiple independent machines arearranged in series along a working fluid flow path. This has theadvantage of generating much larger total fluid pressure rise or dropthan is possible across individual machines.

Where the first primary embodiment is used in a thermodynamic cycle,multi-staging can increase overall cycle pressure ratios, which is avaluable improvement for end uses where individual machines areconstrained in allowable total diameter or allowable maximum rotorspeed. Where the two halves of the first primary embodiment are eachused to handle their own distinct fluid streams, one stream can navigatemultiple machines in series while the other stream is split up totraverse those same machines in parallel, so that large flow ratesacross small pressure differences can be converted into small flow ratesacross large pressure differences or vice-versa.

(FIGS. 37 through 38B) Multi-staging is particularly useful toapplications of the second primary embodiment, whose maximum fluidpressure rise or drop is inherently limited. Multiple machines can beoriented on a common rotational axis 325 so as to use a commoninput/output shaft 326. Furthermore, a system of valving 327 can allowfluid flow to selectively switch from series 328 to series/parallel toparallel 329 flow paths through the machines to provide a kind ofmulti-speed fluid transmission, which may prove useful for groundvehicle propulsion.

The third primary embodiment already incorporates multi-staging into itsbasic configuration. Total fluid pressure change across this embodimentis limited only by the number of inward-and-outward radial cycles it cancontain. If mechanical gearing is used to provide the third primaryembodiment with a single-shaft power input/output capability, a valvingsystem similar to that proposed for the second primary embodiment can beused to selectively switch between series and parallel flow paths asneeded to provide a multi-speed fluid transmission.

-   -   6.2.6—Structural Bridging Across Flow Paths

(FIGS. 15A, 15B, 17A and 17B) Within all primary embodiments, radialflow passages through impellers and bladeless annular volumes havegreater axial width at smaller radii and lesser axial width at largerradii, so as to provide approximately constant flow cross-sectional areathroughout the machine (machines handling compressible fluids can usereduced flow cross-sectional areas in high-pressure sections). If eachof the slower rotating structures in the first primary embodiment hasinner and outer impellers, the wider flow passages through the innerimpellers and vortices add up to a machine having a large axialdimension near its hub. For a more compact package, inner impellers canbe eliminated from every other rotating structure and replaced by flowpath bridges 330. Flow path bridges must link together the rotorsections that would otherwise be linked, and carry the structural loadsthat would otherwise be carried, by the blade sets in the eliminatedimpellers. The bridges must have sufficient stiffness to maintainalignment between the rotor sections they link together, and mustwithstand the centrifugal loads associated with their rotational speeds,all while creating the smallest possible flow disturbances in the fluidpassages. For example, each bridge might consist of two or more crossinghelical elements, which carry hoop stress resulting from centripetalloading and cancel each other's tangential component of tensile force.Their bulk is concentrated around a single radius, which is the radiusof the leading edges of the impeller blades they eliminate. At thatradius, the bridges are rotating at nearly the same speed as the fluidthat is flowing past them, so drag on the flow is minimized. For everyinner impeller that is replaced by a flow path bridge, two adjacentradial flow passages are eliminated and the machine's axial dimensionshrinks by an amount slightly less than the width of the two passages.

(FIGS. 19B, 22A through 23B) Reduction of overall axial dimension may bemore important for the second primary embodiment than for the first,because the second may be in greater need of multi-staging and becausethe multiple stages must share a common rotational axis if they are touse a common input/output shaft. To that end, the second primaryembodiment's axial dimension can be minimized if it uses only onespin-up impeller 250 to spin up fluid and one spin-down impeller 276 toslow it back down, in addition to the process impeller 274 that providespower input/output. The vortices that separate the three impellers willlikely have large exit/entry spin ratios, possibly resulting in highfluid shearing rates on flow surfaces within those sections, aspreviously discussed. To reduce those fluid shearing rates, a thirdmid-speed rotating structure 280 that has flow path bridges 331 but noimpellers can be inserted between the low-speed outer structure and thehigh-speed input/output impeller and shaft. This mid-speed structure,which performs no significant energy transfer with the fluid, willsimply freewheel in the flow and provide annular walls of intermediateangular velocity within the fluid vortices, reducing fluid shearingrates at those walls. Machines whose fluid vortices have very highexit/entry spin ratios may benefit from using more than one mid-speedfreewheeling rotor.

(FIGS. 25B, 29A and 29B) Although the third primary embodiment need notdevote a significant fraction of its total axial extents to fluidspin-up and spin-down operations, it may need to employ fluid vorticesof large exit/entry spin ratios within its inward and outward radialcycles. This embodiment may therefore also benefit from the addition ofa mid-speed rotating structure 313 incorporating flow path bridges 332for the same reason: to reduce the fluid shearing rates at annularwalls. Again, machines whose fluid vortices have very high exit/entryspin ratios may need more than one mid-speed structure.

-   -   6.2.7—Icing and Flash Boiling in Low-Pressure Zones

(FIGS. 12, 20 and 26) In each of the three plots of enthalpy vs. fluidradius representing the three primary embodiments (which all showcompressor flows), there is a noticeable enthalpy drop 270, 333, 334downstream of the intake 269, 295, 316 and immediately upstream of thefirst steep ascent 265, 298, 335 of the enthalpy curve. In each of theseembodiments, working fluid pressure is dropping well below intakepressure at some point along the flow path. In all three cases, thelargest pressure drop occurs across the fluid vortex that is immediatelyupstream of the inner process impeller, and is the consequence of usingthat vortex to spin up the fluid to those high impeller speeds. In allthree cases, the result is a zone of fluid at the inner radii of theprocess impeller whose pressure is well below the machine's intakepressure. Wherever local fluid pressure is lower than at intake, icingcan occur if the working fluid is moist atmosphere, or flash boiling canoccur if the working fluid is a liquid near its boiling point.Atmospheric icing can result in ice accumulations on flow surfaces,which can disturb smooth fluid flow and/or cause mass imbalance inrotors. Flash boiling can choke off fluid flow rate and/or causephysical damage to flow surfaces.

(FIGS. 39 and 40) To prevent the undesirable effects of low pressures incertain working fluids, two methods are useful: (1) within the spin-upsection of the machine, reduce the outer/inner radius ratio of eachfluid vortex 336 below that of the spin-up impellers 337 until fluidpressure at each vortex inner radius 338 no longer drops below intakepressure. This method results in each spin-up impeller (and the innerprocess impeller) being positioned at larger radii than the lastupstream impeller. (2) Employ multi-staging to pre-pressurize theworking fluid. This method requires the low-pressure compressor to dowithout a spin-up section and instead rely on a slower-speed processimpeller 339 having a very large outer/inner radius ratio, paired withan outer-radii spin-down section 340. Without a spin-up section, thiscompressor has no significant low-pressure zones, and itslarge-radius-ratio process impeller can build up enough fluid pressureto eliminate undesirable effects within the high-pressure compressordownstream.

6.3) Angular Velocity Regulators

-   -   6.3.1—Role & Operation

In the previous descriptions of basic impeller-vortex assemblies,working fluid is assumed to posses some tangential velocity T prior toentering the first impeller. Indeed it is true that impeller-vortex flowpaths are only capable of transitioning fluid between low and high-speedrotation, not between zero and high-speed rotation.

Since it can be assumed that fluid entering the intake of avelocity-stepping turbomachine will have negligible net rotation aboutthe machine's axis, and since the use of a spiral intake structure tocreate that rotation would undesirably couple rotational speed to fluidflow rate, some means for transitioning fluid between zero and low speedrotation must be included as part of the present invention. This is therole of the angular velocity regulator.

From a functional perspective, the angular velocity regulator can bethought of as a combination of a pressure regulating valve and a nozzle,in that it imposes a specific quantity of fluid pressure drop to theflow passing through it, and uses that pressure drop to accelerate theflow to a corresponding exit velocity.

The angular velocity regulator must apply a tangential velocity to thefluid flowing through it, and that velocity must be proportional to thespeed of the slowest rotating structure in the machine, to eitherfacilitate smooth, straight flow into the first upstream spin-upimpeller or to cancel out the rotation of fluid that has left the lastdownstream spin-down impeller. These tasks are needed to maintain asteady power balance between the driving and driven impellers of theslowest rotating structure. These tasks must be consistently performedacross a wide range of possible fluid flow rates as well as duringcomplete flow reversal, in keeping with the claimed flexibility of thepresent invention.

(FIG. 41A) The regulator consists of an axisymmetric set of overlappingvanes 341 centered on the machine's rotational axis and placed in theflow of working fluid 342, which all pivot around their leading edges343 and are all generally angled toward the direction of intended fluidrotation. The spaces between each adjacent pair of vanes form convergingflow passages 344, this being the only use of such passages invelocity-stepping turbomachines. A regulating force 345 is applied toeach of the vanes, pushing them to pivot toward more tangentialorientations, thereby narrowing flow passages and increasing flowobstruction. Flow obstruction in turn causes pressure build-up 346upstream of the vanes, pushing them to pivot toward more radialorientations, thereby enlarging flow passages and decreasing flowobstruction. Once equilibrium is achieved, regulating force iscounter-balanced by the pressure difference across the vanes, and thatdifference is converted into fluid tangential velocity 347 via theconverging flow passages, so control over regulating force establishescontrol over fluid tangential velocity. In most end uses, regulatingforce should be largely independent of vane pivot angle, because vanepivot angle will vary with fluid flow rate while fluid angular velocityleaving the regulator should generally be independent of fluid flowrate. The pivoting range of motion should generally be as small aspossible, and can be reduced by locating the regulator vanes within aflow section of enlarged cross-section area. NOTE: in this applicationof converging flow passages, flow-pressure coupling is not a concernprovided that regulating force is independent of vane pivot angle, andvelocity-dependent loss will be proportional to the pressure differenceacross the vanes, which is a very small percentage of the total pressuredifference across the entire machine.

Since the regulator's exit velocity must be proportional to the speed ofthe slowest impellers, regulating force must vary with impeller speed.This can be accomplished with hydraulic or pneumatic force applicationby using a valve to maintain hydraulic or pneumatic system pressureproportional to total fluid pressure rise or drop across theturbomachine, because regulating force should be kept proportional tototal machine pressure rise or drop (both are proportional to the squareof impeller speed). If electro-mechanical force application is used, asensor must provide impeller speed information to an electronic controlunit, which will calculate the necessary regulating force.

Angular velocity regulators can be mounted to the stationary casing withregulating force applied by hydraulic, pneumatic, or electro-mechanicalmeans or by calibrated spring, or they can be mounted to the slowestrotating structure with regulating force applied by electro-mechanicalor centrifugal means or by calibrated spring. The type of regulator usewill determine the best type of mount and regulating force. Stationaryregulators must control the angular velocity of fluid entering the firstupstream spin-up impeller so as to facilitate smooth flow into thoseimpeller blades. Where stationary regulators are used without flowreversal capability, fluid angular velocity leaving the last downstreamspin-down impeller can be dissipated into the machine casing. Rotatingregulators must induce a fluid tangential motion against the rotationaldirection to cancel out the rotation of fluid leaving the lastdownstream spin-down impeller, in order to counter-balance the shaftpower consumption caused by non-rotating fluid entering the firstupstream spin-up impeller. Where rotating regulators are used withoutflow reversal capability, the blades of the first upstream spin-upimpeller can use simple rounded leading edges (much like the leadingedges of a subsonic aircraft wing) to accommodate varying fluid approachvectors. Regardless of the mounting location, it is generally desirableto locate the vanes of the angular velocity regulator at the trailingedges of a rotating or stationary blade set or some other axisymmetricset of barriers to tangential flow. Otherwise the fluid entering theregulator may already have some unknown angular velocity relative to thevanes, which would add to, or subtract from, the angular velocityimparted by the regulator, compromising the known relationship betweenregulating force and the regulator's exit velocity.

(FIG. 41B) Under reversed flow 348 conditions, the angular velocityregulator will lose the cross-vane pressure difference that opposes theregulating force. As a result, those vanes will pivot to a closedposition 349 and will become a barrier to reversed fluid flow. Forapplications of the present invention in which reversed flow isundesirable, the regulator can therefore double as a one-way valve forworking fluid. Where reversed flow is desirable, each vane of theregulator will contain a smaller reversing flap 350 that also pivotsabout its leading edge and opens in a direction opposite that of thevane. The reversed flow that closes the vanes will open the reversingflaps to provide flow paths 351 through the regulator. The flaps willpivot to align with approaching flow vectors, so as to smoothly guidefluid into the blades 352 or other circumferential barriers located(now) downstream. In this way reversing flaps transition reversed flowfrom a state of relative angular velocity entering the regulator to astate of zero relative rotation leaving the regulator (a sequenceopposite that during normal flow). Although such a transition involvesturbulent kinetic energy dissipation 353 downstream of the flaps and istherefore less energy efficient than the equivalent performed by a setof diverging flow passages, once again the total energy lost in thetransition is a very small percentage of the total energy transfer ofthe entire machine, and the flow-pressure coupling associated withdiverging flow passages can be completely avoided.

-   -   6.3.2—Regulators as Speed Governors

Many end uses of the first and third primary embodiments, such as thoseinvolving a thermodynamic cycle, may require a speed governor to controlimpeller speeds within the machine. The angular velocity regulators canserve double-duty as speed governors. By controlling the angularvelocity of fluid entering or leaving the slowest rotating structure,regulators can control that structure's impeller power balance andtherefore its rotational speed (see previous discussion of restoringforces associated with impeller speed deviations). As the speed of everystructure in a velocity-stepping turbomachine is some constant multipleof the speed of the structure enclosing it, control over the sloweststructure's speed equals control over all speeds in the machine. In thisapplication regulating force is determined by desired rotor speed, notactual rotor speed. NOTE: for machines intended to handle reversed flow,two regulators must be equipped to act as speed governors, one in eachflow direction.

Because the present invention is not constrained by flow-pressurecoupling, it can easily perform thermodynamic cycles of variablepressure ratio (a potentially valuable feature) if provided with angularvelocity regulators that can provide variable speed governing. Thisrequires active manipulation of the regulating force acting on the vanesof the regulators, the force being in proportion to the desired impellerspeed. Active manipulation of regulating force can be accomplished via acontrol valve if force application is hydraulic or pneumatic, or it canbe accomplished via an electronic control unit if force application iselectro-mechanical. Since the control valve or ECU will be stationary,the angular velocity regulator being manipulated should also bestationary, unless the communication path from control to regulator canjump from stationary to rotating parts (e.g. an electrical signal).

For end uses of the present invention in which speed governing isnecessary but variable speed governing is not, regulating force can beapplied to regulator vanes via calibrated springs. The springs canprovide a constant, pre-determined force, which equals a steady andknown regulator exit velocity, and therefore a known governed speed.Regulators using calibrated springs can be stationary, or they can berotating if vanes are mass-balanced about their pivots to eliminate anycentrifugal effects.

-   -   6.3.3—Regulators Using Centrifugal Regulating Force

(FIGS. 11B, 14A, 14B, 25B, 28A and 28B) Any rotating angular velocityregulators that do not double as speed governors can use centrifugalforce as regulating force, a method far simpler than hydraulic,pneumatic, electro-mechanical or calibrated spring methods. If regulatorvanes are mounted to the slowest rotating structure such that theirpivot axes are substantially parallel to the rotational axis, and ifeach vane has some mass imbalance about its pivot axis, the centrifugalforce associated with the structure's speed will seek to pull the vane'sheavy end away from the rotational axis. Vanes 354 which handle inwardradial flow already locate their bulk on the correct side of their pivotaxes, and vane mass can be fine-tuned to provide a force correspondingto the proper fluid angular velocity output. Vanes 355 that handleoutward radial flow locate their bulk on the incorrect side of theirpivot axes, and so will each include a counterweight on the oppositeside of their pivots. Counterweight mass can be fine-tuned to provide aforce corresponding to the proper fluid angular velocity output. Thecentrifugal method is effective across a wide range of impeller speedsbecause both regulating force and centrifugal force are proportional tothe square of impeller speed; so the regulator's exit velocity canalways be kept proportional to impeller speed.

-   -   6.3.4—Regulators for Second Primary Embodiment

(FIGS. 19B, 37 and 42) The second primary embodiment of the presentinvention imposes unique requirements on its angular velocityregulators. Speed governing is not required, as the input-output shaftspeed will determine all other speeds. Unfortunately, the secondembodiment cannot employ rotating regulators with their simple option ofcentrifugal regulating force unless the machine is being used strictlyas a turbine. This limitation is due to the radial distance between thespin-up and spin-down impellers, which would preclude effectivecounter-balancing of the shaft power produced by an outer-radii rotatingregulator when the machine is operating as a compressor. Stationaryregulators must therefore be used if the second embodiment is to operateas a compressor. Where flow reversal capability is required, twostationary regulators will be needed. Since the architecture of thesecond embodiment allows the two regulators to be in proximity to eachother, the two can share a common hydraulic, pneumatic orelectro-mechanical system in which a linkage 356 applies regulatingforce 357 on one regulator by pushing against the fully closed positionof the other. Regulating force applied to the small-radii regulator 358must be less than that applied to the large-radii regulator 359 due tothe reduced fluid angular velocity required of the former versus thelatter, so the common mechanism must apply force to the latter through alonger effective lever arm 360, and to the former through a shortereffective lever arm 361.

6.4) Working Fluid Leakage

(FIG. 43) The present invention employs multiple rotating structuresthat are typically enclosed inside one another and are contained in acasing. Because relative motion exists between all of these components,some degree of mechanical clearance or gap must separate each rotatingstructure from its neighbors and from the casing. Such gaps 362inevitably become pathways for working fluid leakage 363, which isdriven from higher fluid pressures at the machine's outer radii 364toward lower fluid pressures at its inner radii 365. Within the firstand third primary embodiments, working fluid will also leak 366 acrossthe plane of symmetry (between turbine and compressor sides) due topressure differences between the sides. In the third primary embodiment,working fluid will leak in the axial direction from the machine'shigh-pressure end to its low-pressure end. Leakage of working fluid fromhigher to lower-pressure regions is undesirable as it represents a wasteof energy and a loss of device efficiency. Where the first or thirdprimary embodiments are used to handle two separate streams of differenttypes of fluids, leakage across the plane of symmetry will result incontamination of one fluid type by the other.

(FIG. 25B) This specification does not call out any particular methodfor sealing against working fluid leakage. The best practices used bymanufacturers of gas and steam turbines are likely to be suitable foruse in the present invention. Where efficiency loss is the only concern,the sealing apparatus need only restrict leakage to a sufficiently smallflow rate. Where contamination of one fluid type by another must beprevented, a more effective sealing apparatus may be needed, perhaps oneincorporating an intermediate low-pressure volume into which both fluidscan leak and be separated from one another afterward. Leakage across theplane of symmetry of the first or third primary embodiments can also beslowed through use of small-diameter shafts 367 to connect impellers inone half to their symmetrical counterparts in the other half, as shaftswould present a smaller sealing perimeter than large-diameter discs.

6.5) Heat Transfer Through Machine Structure

Just as pressure-driven leakage of working fluid through clearances willadversely impact machine efficiency, so too will temperature-drivenconduction of thermal energy through rotating structures and casing.Whenever compressible working fluids are used in the present invention,higher fluid temperatures will accompany higher pressures at outer radiiwhile inner radii host lower fluid temperatures and pressures. Likefluid leakage, thermal energy will flow radially inward. In the thirdprimary embodiment, thermal energy will also flow axially throughrotating structures from the high-pressure end of the machine to thelow-pressure end.

(FIG. 11B) Thermal energy conduction should generally be minimized inpursuit of the highest possible machine efficiencies. The mid-radiuscavities 368 shown within several rotating structures of the firstprimary embodiment assist toward that goal: in addition to reducingstructural mass, the cavities serve to reduce the solid cross-sectionalareas of the structures at those radii and therefore restrict conductiveheat flow from outer to inner radii. A further step might be theinsertion of insulating material or baffle structures into thosecavities, unless they contain a vacuum, to block fluid convectioncurrents whose motion would be greatly assisted by centripetalacceleration. Where feasible, rotating structures can be constructed oflower-conductivity materials such as fiber composites. These structurescan also be built up from multiple concentric or axial sections that arebolted together so as to place multiple low-conductivity mechanicaljoints along the thermal conduction path, where allowed by stressconcerns.

6.6) Bearings

(FIGS. 44A and 44B) Each independent rotating structure in avelocity-stepping turbomachine must be carried on its own set ofbearings so that it may rotate at its own unique speed, and thosebearings must maintain component alignments within sufficiently smalltolerances to enable sealing systems, efficient blade tip clearances,etc. Bearings may be subjected to axial loads resulting from bladeforces or from fluid pressure distributions on rotating structures.Being located in the hub of each rotor, bearings are surrounded by thelowest fluid temperatures in the entire machine. Two different bearingsystem architectures are available: (1) The rotor-on-axle system inwhich all rotating structures 369 are carried on a common axle 370, thataxle usually being integrated into the machine casing 371 except in thesecond primary embodiment. Each bearing's speed equals the full angularvelocity of the structure it carries. (2) The rotor-on-rotor system inwhich each rotating structure 372 is carried on the structure 373 thatencloses it, the casing 374 carrying the entire assembly. Each bearing'sspeed equals the angular velocity difference between the structure itcarries and the next one out.

(FIG. 19B) The rotor-on-axle bearing system has the advantage of acommon stationary axle, which may be useful as a conduit for continuouslubricant flow to the bearings if needed, or as a mounting location forspeed sensors. The rotor-on-rotor bearing system has several advantages:(1) rolling-element bearing DN numbers can be lower because bearingsonly bridge the speed differences between adjacent structures, andbecause bearing diameters can be smaller if they don't need to fitaround a common axle, (2) centrifugal stresses in the hubs of rotatingstructures can be lower because those hubs need not include centralholes to accommodate a common axle, and (3) pressure-driven leakage flowthat would otherwise seek to pass through central holes in each hub isblocked by solid hubs. The drawings show the first primary embodimentand half of the third primary embodiment as using the rotor-on-rotorbearing system. The second primary embodiment and the other half of thethird primary embodiment are both shown as using a modification of therotor-on-axle system in which the high-speed input/output shaft 278 actsas a common axle. The reader should note that complex rotordynamicinteractions could occur during operation of the rotor-on-rotor systemor the modified rotor-on-axle system.

Although the drawings in this specification show rolling-elementbearings, the operating conditions associated with certain end uses ofthe present invention may favor other bearing types such as aerostatic,hydrostatic or hydrodynamic fluid film bearings or active magneticbearings.

6.7) Structural Failure Containment

Moving parts within turbomachines generally rotate at high speeds,frequently at the highest speeds allowed by material stress limits.These parts can be under huge centrifugal loads and can contain enormousamounts of kinetic energy when rotating at speed. If a high-speed movingcomponent suffers structural failure during machine operation, fragmentsof that component are thrown radially outward in all directions at thoseenormous kinetic energy levels. These high-energy fragments can shrednearby people and equipment, if allowed to leave the machine's outercasing. Structural failure containment is therefore an important safetyfeature of any turbomachine.

The basic architecture of the present invention provides a key externalbenefit in this regard. The primary embodiments generally enclose fasterrotating structures within multiple slower rotating structures, as ameans to reduce the mechanical complexity required for a certainconfiguration of radial-flow impellers. This arrangement puts thefastest and therefore highest-failure-risk structures deep in the heartof the machine and surrounds them with multiple layers of slower,lower-stress structures. Should one of the inner, faster rotatingstructures disintegrate under centrifugal force, the large kineticenergy of its fragments can be absorbed into the destruction of theslower surrounding structures before reaching the casing. The casing cantherefore do without most or all of the structural reinforcement thatwould otherwise be needed to guarantee failure containment. The slowerrotating structures can perform double-duty as sacrificial containmentbarriers.

6.8) Noise

High noise levels have long been an operational issue for many types ofturbomachines. Chief among the causes is the dynamic fluctuationoccurring in the flow pattern around each blade (rotating andstationary) every time it passes through the wake of an upstream blade.Because the blades in a set are usually closely spaced, and becauseturbomachines frequently operate at very high RPM, each blade passesthrough many, many other blade wakes every second. The resultinghigh-frequency fluctuations around each blade give rise to the loud,high-pitched whine that is associated with many types of turbomachine.Some of the high acoustic frequencies present are known to causediscomfort to people.

The present invention offers two crucial improvements toward the goal ofnoise reduction: lower wake passage frequencies, and wake dissipationwithin bladeless annular volumes. Wake passage frequencies are lowerbecause each impeller is only moving moderately faster or slower thanthe immediate upstream impeller. If the speed difference between thewakes and the blades passing through them is small, the wake passagefrequency is low. Lower acoustic frequencies are less likely to beunpleasant to people nearby.

All blade wakes are significantly dissipated within the bladelessannular volumes that are downstream of almost every impeller. This islargely because each fluid particle takes a relatively long spiralingpath through each volume, during which the flow velocity deficits withinblade wakes can be more broadly distributed throughout the adjacentfluid before the downstream impeller entrance is reached. If each bladeexperiences weaker wakes from upstream blades, flow fluctuations areless intense and generate less noise.

7.) END USES OF THE INVENTION

Practical applications of velocity-stepping turbomachines that have beencontemplated by the inventor as of the date of this document are listedhere.

Where the present invention is configured as a reversible brayton cycleheat engine and/or heat pump, engine efficiency and heat pumpperformance coefficient can both closely approximate that of the idealbrayton cycle, with built-in tolerance of independent variations in flowrates and cycle pressure ratios. Some practical end uses are: (1) anopen-cycle engine whose heat source is fuel combustion or other chemicalreaction, geothermal heat or concentrated sunlight. (2) A closed-cycleengine whose heat source is a nuclear reaction or concentrated sunlightin space, or whose heat source and sink are marine thermal layers as inan OTEC system. (3) An open-cycle heat pump and/or air conditioner forhouses and other buildings, its open atmospheric cycle eliminating oneof its two heat exchangers and broadening its range of useful climates.(4) An open-cycle refrigerator for residential or commercial use.

Where the present invention is constructed as a reversible heat engineand/or heat pump that can operate between ambient and cryogenictemperatures, high efficiency and/or performance coefficient andoperational flexibility are retained. Some practical end uses are: (1)Liquefaction of natural gas and maintenance of LNG temperatures viarefrigeration, including energy retrieval during re-gasification. (2)Liquefaction of all common industrial gases and maintenance of liquidtemperatures via refrigeration, including energy retrieval duringre-gasification. (3) Maintenance of cryogenic superconducting electricalelements environment via refrigeration. (4) Small or large-scale energystorage using liquefied air, in which energy is stored using anopen-cycle cryogenic refrigerator, and is retrieved using that samerefrigerator operating in reversed flow as an open-cycle cryogenic heatengine.

Where the present invention is configured as a high-efficiencysingle-stage or multi-stage reversible pump/motor, some practical enduses are: (1) single-shaft power input from electric motors or output togenerators. (2) Hydraulic or pneumatic tractive powering of cars,trucks, trains, etc. with built-in regenerative braking capability, andwith built-in multi-speed transmission capability if pump/motor ismulti-staged with series-to-parallel valve switching. (3) Hydraulic orpneumatic power distribution within vehicles, equipment, factories orother power-intensive mechanical systems. (4) Hydroelectric turbineswith built-in flow reversal capability for energy storage. (5) Gascompressors and liquid pumps for pipeline transmission, industrialprocesses, etc. (6) Fuel and oxidizer turbopumps for liquid-fueledrocket engines.

Some other miscellaneous end uses are: (1) High-efficiency distillationof seawater or contaminated water and extraction of water from sewage,by using a multi-staged compressor/turbine assembly first to reducesource liquid pressure until water content boils off at ambienttemperatures, and second to use centrifugal means (and possiblyfractional distillation) to separate water vapor from contaminantscarried with it, and third to re-pressurize the pure vapor and liquidwater. This system must of course include a heat exchanger to transferthe latent heat of vaporization from condensing water vapor to boilingsource liquid. (2) Condensation of atmospheric water vapor for locationswhere other water sources are not practical or available, by usingmulti-staged intercooled compression (and subsequent expansion) ofatmospheric air, or by using refrigeration. (3) Separation ofatmospheric air to produce pure constituent gases. (4) Separation ofatmospheric carbon dioxide at a viable sequestration site usingmulti-staged intercooled compression (and subsequent expansion) ofatmospheric air, thereby eliminating the need to transport the gas fromconcentrated source (power plant) to sequestration site.

1-22. (canceled)
 23. A method of operating a turbomachine as a pump orcompressor, comprising: providing a pump or compressor that ingests afluid flow and directs the flow to enter a first process impeller atradius A, the flow then exiting said first impeller at a radius B andentering a first bladeless annular volume, the flow then exiting saidfirst volume at a radius C and entering a second impeller, said secondimpeller rotating at a slower revolution per minute than said firstimpeller, where said first impeller is being driven by a motive force,wherein all impellers have a common rotational axis when each radii ismeasured from said axis, and wherein said radius C is larger than saidradius B, and said radius B is larger than said radius A.
 24. The methodof operating a turbomachine of claim 23, where said second impeller isan additional process impeller from which the flow exits at a radius Dinto a second bladeless annular volume, the flow then exits said secondvolume at a radius E, wherein said radius E is larger than said radiusD, and said radius D is larger than said radius C, said second impelleris being driven by a motive force.
 25. The method of operating aturbomachine of claim 23, further comprising: the flow being directedthrough one or more additional process impellers after exiting saidsecond bladeless annular volume, wherein the flow is directed through abladeless annular volume in a radially outward direction after exitingeach respective process impeller, and wherein each process impeller isdriven by a motive force.
 26. The method of operating a turbomachine ofclaim 23, where said second impeller is a spin-down impeller from whichthe flow exits at a radius F into a second bladeless annular volume, theflow then exiting said second volume at a radius G, wherein said radiusG is larger than said radius F, and said radius F is smaller than saidradius C, where said second impeller generates an output motive force.27. The method of operating a turbomachine of claim 26, furthercomprising: the flow being directed through one or more additionalspin-down impellers after exiting said second bladeless annular volume,wherein the flow is directed through a bladeless annular volume in aradially outward direction after exiting each respective spin-downimpeller, said impellers and volumes being axially adjacent to eachother along the flow path, each spin-down impeller generating an outputmotive force.
 28. The method of operating a turbomachine of claim 26,wherein the flow instead exits said second bladeless annular volume at aradius H, said radius H being smaller than said radius F, and the flowis then directed through one or more additional cycles of radiallyoutward flow through a process impeller and bladeless annular volumefollowed by radially inward flow through a spin-down impeller andbladeless annular volume, said radial flow cycles being axially adjacentto each other along the flow path, and wherein each process impeller isdriven by a motive force and each spin-down impeller generates an outputmotive force.
 29. The method of operating a turbomachine of claim 26,further comprising: the flow being directed through one or more spin-upimpellers prior to entering said first process impeller, wherein theflow is directed through a bladeless annular volume in a radially inwarddirection after exiting each respective spin-up impeller, wherein saidimpellers and volumes are axially adjacent to each other along the flowpath, and each spin-up impeller is driven by a motive force.
 30. Themethod of operating a turbomachine of claim 28, further comprising: theflow being directed through one or more additional process impellersduring the radially outward legs of each radial flow cycle, the flowbeing directed through a bladeless annular volume in a radially outwarddirection after exiting each respective process impeller, wherein eachprocess impeller is driven by a motive force.
 31. The method ofoperating a turbomachine of claim 23, where a fluid angular velocity isuniform within one or more impellers.
 32. The method of operating aturbomachine of claim 23, where one or more impellers are being drivenby or are driving each other or adjacent turbomachines.
 33. A method ofoperating a turbomachine as a motor or turbine, comprising: providing afluid motor or turbine that ingests a fluid flow and directs the flow toenter a first impeller, the flow then exiting said first impeller at aradius J and entering a first bladeless annular volume, the flow thenexiting said first volume at a radius K and entering a second processimpeller, the flow then exiting said second process impeller at a radiusL, said second impeller rotating at a higher revolution per minute thansaid first impeller, said second impeller generating an output motiveforce, wherein all said impellers have a common rotational axis witheach radius being measured from said axis, and wherein said radius L issmaller than said radius K and said radius K is smaller than said radiusJ.
 34. The method of operating a turbomachine of claim 33, where saidfirst impeller is an additional process impeller, the flow initiallyentering a second bladeless annular volume at a radius M and thenexiting said second volume at a radius N to enter said first impeller,wherein said radius M is larger than said radius N, and said radius N islarger than radius J, and where said first impeller generates an outputmotive force.
 35. The method of operating a turbomachine of claim 34,further comprising: the flow being directed through one or moreadditional process impellers prior to enter said second bladelessannular volume, wherein the flow is directed through a bladeless annularvolume in a radially inward direction prior to entering each successiveprocess impeller, and where each process impeller generates an outputmotive force.
 36. The method of operating a turbomachine of claim 33,where said first impeller is a spin-up impeller, the flow initiallyentering a second bladeless annular volume at a radius P and thenexiting said second volume at a radius Q to enter said first impeller,wherein said radius P is larger than said radius Q and said radius Q issmaller than said radius J, and where said first impeller is driven by amotive force.
 37. The method of operating a turbomachine of claim 36,further comprising: the flow being directed through one or moreadditional spin-up impellers prior to entering said second bladelessannular volume, wherein the flow is directed through a bladeless annularvolume in a radially inward direction prior to entering each successivespin-up impeller, wherein said impellers and volumes are axiallyadjacent to each other along the flow path, and each spin-up impeller isdriven by a motive force.
 38. The method of operating a turbomachine ofclaim 36, wherein the flow enters said second bladeless annular volumeat a radius R, where said radius R is smaller than radius Q; the flowhaving already been directed through one or more additional cycles ofradially outward flow through a bladeless annular volume and a spin-upimpeller followed by radially inward flow through a bladeless annularvolume and a process impeller, said radial flow cycles being axiallyadjacent to each other along the flow path, wherein each spin-upimpeller is driven by a motive force and wherein each process impelleris generating an output motive force.
 39. The method of operating aturbomachine of claim 36, further comprising: the flow being directedthrough one or more spin-down impellers after exiting said secondprocess impeller, wherein the flow is directed through a bladelessannular volume in a radially outward direction prior to entering eachsuccessive spin-down impeller, said impellers and volumes being axiallyadjacent to each other along the flow path, each spin-down impellergenerating an output motive force.
 40. The method of operating aturbomachine of claim 38, further comprising: the flow being directedthrough one or more additional process impellers during the radiallyinward legs of each radial flow cycle, the flow being directed through abladeless annular volume in a radially inward direction prior toentering each successive process impeller, wherein each process impelleris generating an output motive force.
 41. The method of operating aturbomachine of claim 33, where a fluid angular velocity is uniformwithin one or more impellers.
 42. The method of operating a turbomachineof claim 33, where one or more impellers are driving or are being drivenby each other or adjacent turbomachines.